I believe what people have stated regarding the Foreign Instrument Pilot is true. I have sat the ground and plan to convert my JAA one so I have full privilages.
To my knowledge to be eligble for the J-1 you can not have more than 100TT. Since you already hold the JAA IR I think you should be over this limit.
I belive that's FAA experience time. I am JAA qualified, so obviously have more than 100 hours! I was told it was FAA PPL maximum - but they didn't even question my about it other than what class of visa and whether I would be instructing over there. Maybe that part lies in the school's issue of the DS2019.
To get an H1 Visa(Right to work) your going to have to prove you have skills that can't be filled by an American so your probably going to have to make a good impression with your employer before talking to an immigration lawyer.
Regarding JAA/FAA Medicals. I know of someone in the same situation who is building time under FAA and licences and the CAA then will review his case on a case by case basis. PM and I'll get you in touch if you guys are interested.
If anyone wants any advice about J1(Exchange visa with right to work whilst studying.) Visas PM me.