Sorry you are going through this, mama. My son just turned 9 mos last Saturday. He, too, is a big guy - almost 23 lbs at his appt on Monday. He will go down fairly easily for my mom for naps, but not so much for papi and me. For night-time, he nurses to sleep with no problem. I actually lay down next to him until he's out. Then do the pillows as you've described. He'll wake up from this after about an hour, though. If I lay down with him and don't get up, he's good for a couple of hours, nursing 2-3 times.
You may want to try altering your night time routine and sticking to it for a couple of days to see if you can change the pattern for him. I'm not suggesting CIO at all, because we don't/won't do it. What I have done with his 4 year old ds (when she transitioned out of our bed at 14 mos), and with him for naps, is pick baby up, soothe baby, lay baby back down. Dd's transition took almost an entire month, but, I think that is because she was much older. And I think I was holding her hand through the crib slats towards the end of that, if I recall.
She also went through a phase where, no matter what stage of sleep she was in, if I went to lay her down, she woke up. That started around 6mos when I went back to work full time. That's when I just decided to go to bed with her every night and then get up after she was down.
Also, other tricks you may try are putting him down with your night shirt, so that he has your scent right next to him. Or laying him down in a pre-warmed spot. If you don't have a lambskin, try warming the bed with a hot water bottle. The baby can otherwise also detect the change in warmth from being close to your body to the cold sheets.
Mama to a dd 10/05; ds 3/09, dd 2/15 and two angels. Expecting another miracle 7/16!