The sleeve surgery removes the part of the stomach that produces intrinsic factor which is necessary to absorb B12 so all post sleevers should be on B12, either injections or sublingual tablets, life long.
Sway you are right in your concerns re PPIs.There is lots of new evidence that they causes B12 deficiency and also magnesium which can cause cardiac arrythmias. I have been testing these 2 on patients on them long term and am quite alarmed at some of their levels.