what happened with your surgery
I had pre-existing post-viral CFS/ME at the time of outpatient surgery that involved a lot of dental anesthetic, some kind of pain killer that I don't recall, and antibiotic. I did not end up in the condition you did, but after nearly passing out after the surgery from what I came to know later to be a cardiotoxic hypotensive reaction, I went on to develop a succession of new symptoms, which later evolved into lowered immunity, more unusual infections, autoimmune manifestations...
I experienced an unusual amount of swelling after the surgery, which was for scar revision. The first noticeable symptom that should not have been a result of the surgery was that my intestines seized up and would not move. This happened withing 24 hours and never resolved until I stopped taking a medicine I had been taking in the lowest dose and had never had any problem with. It was not a very necessary or helpful med, so I just stopped it after a few months of trial and error. From then on, as long as I did not use it I was able to have a bowel movement. With it, I was not, without using the strongest kind of medicine of the kind one could not use on a daily basis. The functioning of my bowels had been permanently altered in some way.
There were skin changes, poor healing, increased PEM. Then a neuromuscular symptom, IBS, cardiac, increased cognitive symptoms. After a few years of new symptoms the preexisting ones tended to worsen and become pervasive rather than post-exertional only.
Much of this began before the days of internet, so information was non-existent for the most part. I was exercising a lot at the time and possibly pushed too hard at times, but more recently I've come to believe that the drugs that were involved in the surgery - the anesthetic, pain killer, and/or antibiotic - one or more of them together were toxic to me or had altered my gut environment in some life-altering way. I needed quite a few dental surgeries in years following and became more sensitive to these same substances at times, yet my experience with them has not been entirely consistent, which has made it hard to say exactly what caused what.
I have 3 kinds of B12 excluding cyano that I am rotating experimentally. I will be trying the oil at some point, which is supposed to be a balanced formula of adeno and methyl. Hydroxy is recommended for those sensitive to methyl.
If you want an oral B formula that does not contain cyano, Swanson Brands makes a good one. A good multi with low amounts of good Bs is Amy Yasko's All In One. You probably know to take iron with Vitamin C for best absorption. Have you tried a good oral iron supplement? I am not sure if it is better to take it with vitamin c supp. or natural, as in orange juice.
Since you have asthma I would recommend that you take a look at a probiotic, biofilm spray that I have been using. It seems to help when I use it frequently throughout the day, spraying the room as well as directly up my nose and in my mouth while breathing in. The original brand was PIP, but they've changed the name:
http://www.p2probioticpower.com/