Good Day Anne,
The book on B12 goes into pretty deep detail about the diff types of B12 shots and rec the methyl but like you said almost all facilities use the cyan version which is slower...
Had chest CT and everything looked good - no tumors or enlargement so for now that's a bit of a peace of mind.
Breathing has been an issue for most of my life - had many spells of shortness of breath - thought it was all allergies and asthma - last few years though it has become a constant thing and I would notice I was laboring doing simple things. From about age 19 I can remember laying down flat and becoming very short of breath - many times I would have to sit up again - nobody could ever explain it but now I think it may have been an early symptom of muscle weakness as I have read others with the same delima...
I am on 30mg x 3 daily for now - dr wants to increase to 60 but trying to let my stomach issues calm down before jumping up. Been on about 3 plus weeks so not sure how long it takes to reduce gas and indigestion issues? I have noticed better breathing from 30mg so that's a plus
Like many I am hoping its not ALS, my neuro does not think so, comforted a good friend some years back that passed at age 43 from that and it was not pretty...

Have a great day!
Randy