Hi there. Many people use variations of shush/pat and if bottom patting is working for you, go ahead! PU/PD is really a worst case scenario kind of move. When I can't comfort in the cot, I pick DD up and comfort her on my shoulder with shush/pat, then I slowly quieten down, lay her back down and keep a hand on her. I felt that I was just messing with her with PU/PD, putting her down just when she had calmed down and it just took way longer than it otherwise would have.
It is normal to have to intervene a few times as he is learning to sleep. This would probably be when he is transitioning sleep cycles. It is also normal for him to need 1 or 2 feeds overnight. The best way to judge hunger is to feed him and see how much he takes. Generally though, if you have fed quite recently, then you could rule out hunger. DD just got over the flu and she too started waking up in the night for feeds. I found it easier to just feed as she fell asleep so much faster & her sleep wasn't too disrupted. Also, with her I always find that when I follow her lead, things like NWs get resolved a lot faster. The few times that I tried to resettle without a feed, she was just up again a short while later asking.
As to crying when you put him down --- are you putting him down awake or drowsy? What do you do before putting him down? Do you have a wind down routine? Some babies also need a little cry as part of their settling to sleep routine. If he wakes at 1.5 hours, the next nap would be 2 hours after that. If you are aiming to have him down in 2 hours A - that is eyes open to eyes closed - then you should go to his room a bit before that - change diaper, swaddle, nap time routine etc - and put him down. It is good to give them 5 -10 minutes to settle. If you find your LO needs more time, go in a bit earlier. If he starts showing sleepy signs way before time, then stretch the A time with some low key activity like walking around.
Hope that helped. x