The gist I saw was that when the binding capacity is low, then the idea is to flood the serum with B12, so that it won't need a carrier anymore. Transcobalamin really has limits in how much it can carry. It is designed to only move 2-4mcg a day, which is our typical RDA.

So the thought is you MIGHT bypass it by having much higher levels. Say over 1000 or even maybe higher.

It would be a waste to get cyano injections IMO, if you are having a impaired methylation status as your test reflects.
You can ask for the hydroxocobalamin type, which the doctor can order, or have methylcobalamin injections compounded for you.
The B12 does not stay around more than 3 days from the shots, so there may be ups and downs in symptoms. This is why oral can be better...some every day mimics how the body receives it from food. You'd have to do high dose orally to get those high levels...close to 5mg a day I would think.

Another thing to look at is the MCV...that would be reported on your CBC results. The MCV will be higher when B12 is not around to help with red cell formation. The cells become larger and that is reflected in the MCV value.

If the MMA is low but homocysteine high, that reflects either, the folate is not methylated and active, a deficiency in glycine which provides the methyl group in the first place, or inactive B6 chemistry. (you would need the special B6 called P5P for that). Methylcobalamin + methylfolate + P5P are the cofactors to convert homocysteine to SAM which then carries that methyl group around the body to the various systems that need it.