A.M.
I have no experience with this but just guessing at the time frame, I'd be suspicious of something in the house. Can you stay at family or friends house for a long weekend and see if his nosebleeds stop? If not, maybe have a family "vacation" and go to Amelia Island and stay in a bed and breakfast and enjoy some time away. There are lots of chemicals in new carpets and varnish on trim etc, that may be causing his mucus membranes to go haywire. Might be worth a try.