weel, you can do your training in the US under the JAA system no problem (obviously apart from the JAR IR)..but if you do the FAA way and convert, you will have to eventually do the 14 ATPL exams...afarid there is no way of getting out of that..
Sure, if you eventually want a JAA Frozen ATPL, sure you'll have to do the exams either way
Afraid I can't comment on phase four of the course as I haven't done the APP course...