I must be doing something wrong.
I would like to make the following suggestions:
1. Change the pee pads in his ex pen frequently with a fresh one - after every use if necessary to keep him clean.
2. Take him outside starting with every half hour and then work your way up gradually to every two hours. Give him no more than 5 minutes to poop or potty when outside. When not successful take him back to his expen. If successful, reward heavily with a couple of treats and lavish praise, and then back to expen
3. I understand it is raining outside. Use an umbrella to cover him and you
4. Get a piece of astroturf or indoor/outdoor carpet (about 5x8 or so) as his outside potty/poop place. Just leave it in place on the ground until the weather drys out. Carry him out to that place or put him on a leash and guide him to that area. No shenanigans or play permitted when taking him out for this task. It's all business on your part.
5. Don't bathe him when bringing back inside, just a quick towel dry if necessary.
6 No rewards when he goes in his expen. Havanese puppies are quick studies, they learn quickly that going outside is where the rewards are.
Puppies of every breed are a handful. Biting and chewing on everything is normal, especially when teething. They soon grow out of it and you will forget about all the work and frustration it was. But Ricky's favorite toy, even at 5 years old, is still an empty, one litre plastic water bottle. He loves that loud crackling sound.
Many people don't want all the work and training associated with a puppy and therefore get a dog that is at least a year old or they will get a rescue. Puppies have their pros and cons, but they sure are cute and they do grow out of it relatively quickly.