Brother, your read on the bloodwork is mostly off in the wrong direction there are bigger things going on than the hematocrit and B12. Let me walk through what I see.
The thing you should actually be looking at: estradiol <25
That's not just "low" that's crashed. The "<25" reading means the assay can't detect anything down to 25 pg/mL, which on a male reference range (where normal is roughly 10-40 depending on assay) means your actual E2 could be anywhere from undetectable up to 25. You're either at the floor or close to it.
This matters because:

The 2 days of "feeling shitty" after dropping the AI wasn't E2 rebounding to normal it was your body responding to crashed E2 that was already crashed. Coming off an AI when E2 is already on the floor doesn't help if your test dose keeps aromatizing into nothing because the AI's effects persist.
Crashed E2 explains several things on this panel: low SHBG isn't only oral-driven (you'd expect it from primo/mast), it's also kept low by crushed E2. Low sodium can be partly E2-related because estrogen affects fluid/sodium retention. The "feeling under-hydrated despite drinking enough" sensation is consistent with low aldosterone signaling, which estrogen modulates.
Crashed E2 also drives joint pain, lipid worsening, libido issues, mood changes, bone density problems, and cardiovascular concerns. You may not notice all of these immediately but they're happening at the cellular level.

The fact that you dropped the AI right before testing tells me you were probably running too much AI on a stack that wasn't aromatizing much to begin with. Mast doesn't aromatize. Primo doesn't aromatize. If you were running test alongside these, the test was the only aromatizing compound, and aromasin/arimidex would have crushed that easily. Dropping the AI was the right move but the damage to E2 is still showing.
What you should do about E2:

Stop any remaining AI completely
Wait 2-3 weeks for E2 to recover naturally as your test continues aromatizing
Retest E2 then preferably sensitive assay if available
Manage by symptoms going forward, not by lab number especially since at this assay you can't even see how low you are

The sodium/hydration thing you raised:
Your read is partially right but you're missing the bigger picture. Sodium 134 with chloride 96 is mild hyponatremia and it's correlated with the crashed E2 estrogen plays a role in sodium and fluid balance through aldosterone modulation. Drinking 1.5 gallons of water with crashed E2 and 5g sodium might genuinely be diluting you because the sodium retention pathway isn't being supported normally.
More sodium will help short-term but the real fix is letting E2 recover. Once E2 normalizes, the same sodium intake will feel adequate.
The hematocrit at 53.5:
Real but probably not your most urgent issue. The framing "hydrating will bring it down" is partially correct but also partially misleading better hydration improves the plasma volume measurement, but actual RBC mass is still elevated. You're running mast/prop without significant erythropoietic suppression, and your previous baseline of 52 suggests you've been at the edge for a while.
Donation is the move here, not just hydration. 53.5 isn't emergent but it's the point where preventive donation makes sense. Once a year is too infrequent at these levels.
Things on this panel that are actually good news:

HbA1c 4.6, glucose 77, insulin <1 your metabolic health is excellent. The low insulin probably reflects fasted state plus possibly low-carb meal timing before draw. Nothing concerning there.
Liver panel completely clean ALT 33, AST 28, GGT 24, ALP 84, bilirubin 0.80. Mast/primo aren't liver-stressful and your numbers reflect that.
Lipids better than your last panel implied. Total 188, HDL 45, LDL 135, trigs 41. LDL is elevated but trigs are great, HDL is adequate. With Lp(a) <10 (low genetic CV risk), your cardiovascular profile is actually reasonable. Better than most guys on cycle.
hs-CRP 0.50 low inflammation, low CV risk by this marker
Kidney function normal, prolactin normal, vitamin D adequate, PSA fine, iron panel balanced

The white count and lymphocyte numbers:
WBC 3.1 with lymphocytes 0.90 is mild leukopenia/lymphopenia. Several possible causes:

AAS-induced (high androgens can mildly suppress some immune cell lines)
Recent illness or stress
Some labs run slightly lower normal ranges than others
Could be related to the dropped primo if you'd been on it long

Not emergent at these values but worth retesting in your next panel to see if it's a trend or a snapshot. If it persists or drops further, that's worth medical attention.
RDW elevated:
Red cell distribution width slightly high (15.8) with normal hemoglobin and slightly elevated hematocrit. Usually reflects variation in RBC size can happen with recent rapid erythropoiesis (which fits your cycle), recent blood loss followed by regeneration, mild iron status changes, or B12/folate issues. Given your story of stopping B12 supplementation, this might actually be the marker showing the B12 effect, not a deficiency per se but the body's adjustment.
The B12 thing:
You stopped because it was high. B12 has very long body stores (years in the liver). Going from "high" to "normal" takes a long time, not weeks. So your concern about adding B12 back in to address something on this panel is probably misplaced your stores are likely still fine. The RDW elevation is more likely cycle-related erythropoiesis than B12 deficiency at this point.
If you want to check, get a B12 + folate level next panel. Adding B12 back supplementation now is fine but probably not addressing anything urgent.
Priority order of what to actually address:

Get E2 retested in 2-3 weeks to confirm it's recovering. If it's still <25 after 3 weeks off the AI, something else is suppressing it. If it climbs to normal range (20-40), you're back to baseline.
Donate blood hematocrit 53.5 with trending upward is the point where donation makes sense as a preventive measure, not just reactive.
Watch the sodium/hydration thing resolve as E2 recovers. If it doesn't, then increase sodium to 6-7g daily and retest.
Lipid management is fine for now LDL 135 is elevated but with HDL 45, trigs 41, and Lp(a) <10, your overall CV risk profile is moderate. Citrus bergamot, fish oil at proper dose (3-4g EPA+DHA), and time will likely bring LDL down post-cycle.
Recheck WBC and lymphocytes next panel to see if the leukopenia is a trend or snapshot.

The framing problem:
Your post focused on the hematocrit and B12, which are minor or non-issues compared to the crashed E2, which you didn't mention at all. This is a common pattern focusing on the visible/expected issues while missing the more important finding. The E2 is the headline of this panel, not the hematocrit.
The good news is that the underlying metabolic and organ health markers are clean. Your liver, kidneys, glucose handling, inflammation markers, and cardiovascular markers (apart from elevated LDL) are all in good shape. Once E2 recovers, most of the abnormal findings here will normalize on their own.
Don't add the AI back unless symptoms specifically warrant it. You probably never needed it on a primo/mast/test stack that's a stack that aromatizes very little.