If you want to become an MEIR instructor you'll find it much easier to find work if you've got an FI as well.
As for the FAA conversion, how close are you to an ATPL? Or is that on hold right now? If you just want the pic time in a multi, you should consider Canada - no visa issues! Plus you'll effectively get an FAA certificate anyway if you want one (after a 20 question test!)
As for your questions, if you've got SEP and MEP then the feds will give you a 61.75 certificate (Google part 61) and allow you to go flying after a flight review with an instructor - they'll include that in your rental checkout so basically you just make sure he's happy. Can you use your type rating instead of MEP? Possibly - just ring a FSDO in the States and ask, then let us know!
Instrument ratings in the US aren't SP or MP, so you might get away with that as well!
You can also get some really good deals in South Africa.