I spread the pillows apart..leaving a 12 inch + space and put the baby there. If your pillows are too big, then buy smaller ones.
if you did that, even if some of the blankets were pretty high, they shouldn't get over his face. or, you can try a co-sleeper till babe gets a little older. once babe is older, you won't need to worry about this kind of thing because he'll be able to get covers and stuff off his face, all on his own, perfectly well.
also, i wanted to point out--you DID wake when he was covered up, and you rescued him, so from that standpoint it seems like you're doing fine. sometimes things happen, baby gets under a blanket or even rolls off the bed--you're alert enough to notice, and that's what really matters most. don't beat yourself up.