It appears that your B12 is marginally low. 400 is the new acceptable low. But other nutrients are affected by long term
proton pump use.

B12
folate
calcium
magnesium
zinc
some other low dose minerals like copper.

I'd recommend getting your kidneys checked, as new information suggests, kidney side effects from proton pump inhibitor use:

Kidney Damage & Failure: Symptoms, Causes, Link to PPIs

Get tests for kidney, and B12, folate. Stop any supplements for at least 3 days (preferably 7) days before testing.

A DNA test also would be a good idea. MTHFR (methylation) failure is fairly common, and would show you if you need methylfolate form of folate.

I'd take methycobalamin 5mg (active B12) once a day for 3 months and get a retest (stopping a few days before the test).
A goal of 1000 or more would be a good result. You can reduce to 1mg a day if you are testing high enough. Always take B12 on an empty stomach so passive absorption can work for you.