You can get injections of methylcobalamin--they have to be
compounded from a special compounding pharmacy.

You don't have to dissolve the Jarrows in the mouth. You can
swallow it with some water on an empty stomach.

There is no advantage to injections. They are typically cyano form, but doctors can special order hydroxcobalamin and it
is a bit easier to convert, and will cost more.

You might have CMT (Charcot Marie Tooth-hereditary) which causes wasting of muscles in the feet (and eventually hands, etc).
Genetic testing is from Athena labs, and quite expensive.