First of all, the exams, because I don't think you understand them. If your aim is an fATPL, then you'll want to do the ATPL exams. There are 14 of them. You say you've got a new job lined up, in which case you'll need to do the studying for these exams through a distance learning course, working evenings and weekends. You should probably allow 12 months for this - it can be done quicker, it may take longer, depending how much time you're able to dedicate to studying each week. You mention the CPL exams and the IR exams - you will not need to do these for an fATPL. The ATPL exams include everything you need to start CPL training and IR training - the CPL exams are for people who don't intend to do an IR, and the IR exams are for people who don't intend to do a CPL.
I'm not exactly sure of the minimum requirements for an FAA IR, but it sounds like a good idea. To convert it to a JAR IR, you'll need to do a minimum of 15 hours flying, as well as completing either the IR or the ATPL exams (the latter in your case).
But my advice to you would be to enjoy yourself as you can with your spare time. I found myself in a similar position 15 months ago, and went to Arizona for 2 months. While I was there, I got a tail-dragger checkout (well, I was kind-of checked out already, but hadn't really been taught properly) and a complex aircraft check-out. I did 5 hours of dual in a twin (didn't actually get the rating because I can't afford to keep it current at the moment), and I got my night qualification done. I did 11 hours of aerobatics (absolutely superb!) I flew around some fantastic scenery, including taking a Super Cub into Sedona airport to get a jeep tour of the beautiful town, and taking the Super Cub into Grand Canyon airport before walking across to the other side of the airport for a helipcoptor tour. I flew a Piper Arrow to Las Vegas overnight, and to Los Angeles for two nights, to do some gambling and sight-seeing. And I made some friends who I'm still in touch with, and hoping to meet up with again when I return to the US for my CPL. Had the time of my life - the only thing I'd change if I could do it again is go somewhere other than the US, simply because it's so easy to do JAR training in the US that it makes sense to hour-build somewhere different just to get more variety.
Have fun!
FFF
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