T.C.
I did a lot of research on this when I had my first child. I was in a similar situation as you an older mom with a new baby. I was also getting a ton of pressure from both grandmas to put cereal in his bottle to help him sleep and because my son was on the smaller side. In all the research I found there was no benefit to giving them cereal earlier than 4 months. When you do give cereal you are to only give it to them on a spoon and never in a bottle. So I would just wait and follow your doctors instructions.
As for gas and fussiness I am dealing with this with my newborn. I switched to Similac Sensitive and it has worked great. So maybe experiment with the types of formula you are using.
It sounds like you are taking good care of the cradle cap, just be careful not to overdo it. It is normal and will run its course.
I put a burp rag under my son's chin to catch the formula. The bibs just don't seem to get up under the neck sometimes. I also tend to change his diaper after I feed him so I will just take a wipe and run it over his neck at that time too.
Good luck and you are doing a great job. Enjoy the time you get with her when she is little, they grow up very quickly.