Julio,
Tough call mate. The UK Mil can get exemptions but I think any one outside Europe is stuffed. (My words, not theirs). If you can prove that the B200 flying was done two crew according to national law etc, you can get an exemption on the 500 hours multi pilot stuff. (ie two crew)
If you can convince an employer to get you a validiation then you have 12 months to do the exams. (that also goes for the Saab endorsed poster).
I am either going to see if I can talk my way round that problem of the ATP skills test, re jobs/employers. The test must be done in a multi crew a/c with a CAA approved examiner. Failing that, I think I will find the cheapest multi crew type to get checked out in. I don't really want to do a full IR again. That's horrendously expensive.