--with the supplementation, that doesn't mean it's all working on the cellular level.

Repairs due to B12 deficiency are typically rather slow, with a lot of ups and downs. It is true that some people feel better quickly, especially in terms of energy levels, but if there's been considerable cellular damage done--and with the former levels you report, I suspect there was--it may take a long time for whatever repairs that can occur to be completed, and when your body gets down to that serious business (and you should be sure to have sufficent quantities of B6, folate, etc., as well--B12 acts in concert with these), don't be surprised if you feel as if you're having "setbacks".

The best way to track this is in long term retrospect--week to week, even month to month. See if there is overall improvement over these time frames.

I do suspect that you do have considerable malabsorption issues, and would probably benefit from higher dosing; you could probably go to 3000-5000mcg/day of methylcobalamin. (There's no known toxicity level of B12.) You might notice a jump in energy or "hyper-ness" if you do.

Most of us like to keep our serum B12 levels very high--in four digits--to make sure our tissues are bathed by a constant high concentration of B12. Those with malabsoprtion/storage issues may have to take the higher does to accomplish this.