Hi Avalon
You have MTRR/MTR mutations which will cause lower B12 levels. From your gut symptoms it could also be you have the h pyroli stomach bug which among other things lowers stomach acid and B12 absorption.
This would cause a large imbalance between Mb12 and methylfolate which could cause'methyl trapping' and some of your symptoms when you attempt to take more folate, as well as causing very poor methylation.
Methylation doesn't work very well with gut problems, and I think you would be advised to have an h pyroli test from your doctor, if you have not already had one (insist on a blood serum test they are the most accurate).
Caledonia's 4R Gut Rebuiding Programme available on her signature will also help.
http://forums.phoenixrising.me/index.php?threads/the-4r-gut-rebuilding-program-summary.25761/
Increasing the MB12 intake will help to crank up the MTRR/MTR although some people need take quite high levels of Mb12 to get the cycle moving.
Heres a diagram of the problem.
http://www.heartfixer.com/AMRI-Outcomes-Non-CV-Autism-Methyl Cycle.htm#MTRR: Methionine Synthase Reductase
MTR Up Regulation (+) and MTRR Down Regulation (+)
"This combination produces a double whammy on methyl-B12. You can’t make it well because MTRR is not functioning well, and any B12 that you do make gets sucked up by the overactive MTR. Here the need to supplement with B12 is greatest." (Heartfixer's comments)
Taking Hcl probably caused the TMG to ramp up methyl by bypassing these mutations using the BHMT short route pathway.