Hi Peike,
Sorry you are struggling right now...I think a lot of people go through this same situation, I know I did.
And it passed with a little hard work.
If your Lo is only sleeping 30-45 minute naps, the key would be to try to go into the room just before the time he starts to stir, and help him through to the next sleep cycle. Try just laying your hand on your Lo's back...rubbing it a little..and if he starts to stir..(if you use pat/shh??) do that to help into the next sleep cycle. Sometimes it only takes the hand on the back, sometimes more.
If that doesn't work....and it sometimes won't in the beginning....and your son wakes up...pat/shh or pu/pd would be the way in which to get him back to sleep. It is a frustrating and time consuming thing to do..I remember spending 45 minutes, 1 hour...all on different days..but it did pay off. So, try using pu/pd or pat/shh..whichever works for your LO best.....if Lo gets too upset, you can take a break to calm each of you down, by changing his diaper, or you leaving the room for a few minutes..and then get back to it--"start as you mean to go on" was always in my head while I went through this. If it happens that he doesn't go back to sleep before his next feed....then feed him at the feed time of course---and then start right back into trying to get him back to sleep.
Once the naps are extended--and they will be! You will be so happy and satisfied that you and your Lo have conquered the short naps
Good Luck, and keep us posted.