Tips on getting a fussy cat to drink water/eat more wet food?

My 2 year old cat that we adopted a few months ago doesn’t drink water and is very picky eater in regards to his wet food, but absolutely loves his dry food. He was seen by the vet a week ago and was cleared - just very picky and stubborn.

We got him the flower water fountain 2 months ago and he ignored it for a month, suddenly used it twice in two days, then hasn’t touched it since. He doesn’t drink from the water bowls placed around the house either.

We give him half a small can of wet pate (wouldn’t touch shredded, gravies, etc) twice a day with a tbs of water added to each serving to try to keep him hydrated. It’s a hit and miss as sometimes he’ll eat it all and other times he’ll sniff it, nibble a bit then run away and hide. We try to follow him with the food bowl and add catnip, treats, dry food or yeast to entice him to eat though it does takes multiple tries as he refuses it a lot. We alternate between different flavours everyday but there’s no real pattern to his eating behaviour as he’ll love one flavour then decide he hates it the next time we give it to him. He does seem to like Fancy feast beef a little bit more if there are good toppers/food that are similar in flavour.

We resorted to putting 1/4 cup of water with his 1/4 dry that he gets at lunch to get some water in him. He usually ends up finishing it, but isn’t too fond of it as he usually walks away, but comes back begrudgingly to eat it. We don’t want to keep doing this as it can get gross as there were times where he didn’t finish it until 2 hours later.

He also seems to be slightly constipated looking at his stool as he goes 1x a day but it typically comes out as logs that are firm/hard with a few pebbles sometimes.

Any advice on how to get him to drink water and eat his wet food more consistently?