I think that shortening the A times might help him to settle more easily. 2hrs of awake time is manageable by some at 4 months, but that's after a long nap or a good night. After a short nap you'll need to cut that back, I would try to have him asleep 1.5hrs after waking tomorrow, and if you get another short nap, cut the next A back by another 10 mins. If it's stressing you out, don't spend time trying to extend the nap with shush-pat, just do a short A time and put him down early for his next nap.
Also, if he is really resisting his wind-down, you can cut it right back. Some of them prefer a really short wind-down, just (for example) into nursery, draw curtains, swaddle, song, into cot (and start shush-pat/PUPD as necessary).