The humping is never going to stop if you don't get him neutered. In my opinion, by not neutering him, you're
never going to get your "little boy" or your old pet back. Once they reach sexual maturity and have an unspayed female near them... that's ALL they will care about and he will be completely focused on that. Basically, everything you described, will probably not change without being neutered. There are millions of dogs being euthanized every single year... and thousands upon thousands in shelters across the US. Do you really want to contribute to pet overpopulation simply to breed? Why do you want to breed? Do you have their health backgrounds? Did you run testing on both dogs to be sure of no genetic defects? Do you know their lineage and pedigree?
I say get them both fixed and enjoy your pets as pets
