Re: 4month boy night time peeing issues
we bought a BBLP. I kept it upside down in a 5 gallon paint bucket beside the bed most of the time. Sometimes I put mircofiber or something inside the BBLP so that it wou;dn't splash so much, but the biggest thing was you have told hold the child just above the potty, aim him down, OR use something on the potty to keep it warmer. The cold can shock a child into peeing, or it can make them not pee and cry and fully wake up. It can vary. Mine would never go in his diaper, no matter what sound I made.
I also made sure there was a large felted, old, wool blanket under the sheets to help waterproof the bed, just in case I tipped over the potty, we sprinkled, etc. We never needed it but was nice not to stress about the mattress getting pee stink.
The BBLP use to fit nicely inside the bucket, I don't know if the design has changed or if other potties would be similar, but having wet bucket with 1-2 dirty dipes by the bed seemed to work best for us.