B12 Deficiency + Methylation Issues

I have genetic mutations that include MTHFR, MTRR and Slow COMT. Due to some of those anything I take related to methylation can throw me into overdrive which means horrendous (or worse than usual) anxiety. For example, I took Creatine a couple of times and it gave me horrible anxiety at the usual maintenance dose of 5g. In my last ditch effort I did ~1g or even a little less and built up over a month or two and now I don't have any side effects.

For B12 issues, I've had symptoms for years. Balance, anxiety, depression, memory issues, clumsiness, pins and needles, and the bottom of my feet stopped registering the floor on occasion at its worst. No doctor thought to say B12 may be an issue, and I spent thousands on doctors, testing, labs, supplements, medications, etc. More importantly, I have been uncomfortable for years and have missed many good opportunities and didn't enjoy other experiences as much as I should have. My level at its lowest was 229. That was a few years ago and I've toyed back and forth with B12, doing shots initially that didn't seem to help (methylcobalamin) and sublingual methylcobalamin and then a Hydroxocobalamin + Adenosylcobalamin combination. It seemed to always give anxiety and still does.

I decided to try again. Due to the genetic issues I think even taking decently moderate doses threw me into overmethylation and/or gave me wake up effects. I took 250mcg sublingual Hydroxocobalamin + Adenosylcobalamin and felt an improvement. I did twice per day and then went up to 500mxg twice per day and then BOOM- anxiety. Horrible anxiety. I dropped back down.

Has anyone else had such an issue? From what ive read you need like 2mg for sublingual. I can't do that.

Since restarting about a week ago I did notice some better energy, improved mood, and dormant memories are coming back. But the improvement isn't 100% all the time - I'll fall into a slump later in the day.