I think you will be ok untill the new year mate, just look for the jills swelling (coming into season) around the new year & check daily , the second you spot either swelling move the hob , if his testes have dropped in the new year get him vasectomised then, but leave him a good 7 / 8 weeks before you atempt to put him with the jills
You may find once he has been done & ready to be introduced back to the jills he will just serve them & be ok , if however he is ragging them all the time even after he has served them , remove him untill the autumn