Is he neutered?
Bathing too often can strip their skin of natural oils that neutralize odors. I would recommend not bathing him so often.
If he smells like fish, it could indeed be his anal glands. You can either search on the internet on how to drain them yourself to take him to the vet to have it done.
As for the potty training issue, you should start with the basics. I would recommend crate training him (if you haven't done so already) and following this schedule to a T until he is fully potty trained:
http://www.darnfar.com/Dog%20Trainin...ng_a_puppy.htm
It's important that you get a crate that is small enough. He should only be able to get up, turn around, and lay down in the crate. If you buy the smallest crate and it's still big enough for him to lay down in one end and not touch the other end, put a cardboard box or tupperware in the back of it.
Please really try and think long and hard before rehoming this little baby. It's not his fault he's not potty trained and doesn't smell good.