I really feel for you having to make this descision. At the time I had to do it it was undoubtably the biggest descision I had had to make as a parent and it's so hard!
There is no need to critisise the OP for the way she is thinking about this, she is just trying to do what's best for her dc, as we all are.
My children both had single vaccines, six months apart, and then six months after that were given a blood test to check their immunity. Ds 1 was completely immune to all three after the one jab, ds2 was immune to measles and mumps but not rubella. Because we were paying a huge amount of money to have the single vaccines, he was able to be vaccinated against rubella again, well before the age he would have got an MMR booster, which has hopefully worked. I decided not to have the blood test again, because if he had shown again not to be immune, I wouldn't have wanted him jabbed three times, and the peadiatrician advised that if he wasn't becoming immune to the vaccine, then he may have a natural protection against it anyway. Plus he had had all the protection he would have got from the MMR at an earlier date and without having to re inject him with vaccines he simply didn't need.
The main reasons I went for single vaccines were that I didn't want the MMR put into my dc's twice when they only really needed it once. I understand that they do it twice to protect a tiny percentage of children that didn't get immunity first time round, but that wasn't a good enough reason to jab my sons twice with something they didn't need.
Also, at the time, Dr Wakefield had not been completely discredited. Whether he was rightly or wrongly struck off, I don't know, but his study was, and still is, the only study to have looked at the children whose parents blame the MMR for their child's autism. That says something to me. The parents who are convinced their child was harmed truly believe that, and it's not like they are saying it just for fun.
I think in your situation OP, I would still not give the MMR. I wish you lots of luck with whatever you decide.