You can still demand feed even when you use formula. The amount on the tin is only a guide, some babies will have a lot more than the guide and others a lot less and it is all normal. Since I don't know why you are FF him, I can only answer your question about him getting sick from feeding closer together based on a well baby, and no they can't get sick from being fed closer than 3-4 hours. I have had my babies feed up to 2 hours apart and no issues at all.

He could be unsettled for a lot of reasons. It could be because he is having to get used to the formula, it could just be because he is at the age where he is getting more wakeful etc and really letting you know he is around. As for holding them, just hold him in your lap, with his head supported in the crook of one arm while you hold the bottle with the other. When mine were very young, I always had them turned in slightly so they were facing my breast more. They don't have to be all the way back, but reclined to about 40-45deg seemed to work best for me. And if you think he is hungry, then give him some more because if he is hungry, no dummy in the world is going to comfort him LOL, just make up the smallest possible amount (60ml from memory) and see if he will take any more. My DS2 would take 120ml - 160ml at a few days old so maybe your little fella is hungry like that too?