do you need it for points? you just joined so it doesn't seem to be adding much. if you have 3 years of experience without them then no need to get a letter
the exchange rate is important when they check. make sure you have MORE than what is needed by 3-400 at all times just in case. otherwise should be good to go
while you're abroad, canada has nothing to do with you. once you move though your company also migrates and you'll have to register with the cra (i'm also an estonian eresident)
no one can tell you that either, it's done by organisations listed by ircc. i suggest you go to the IRCC website and start reading before even thinking of the CRS score
yes if you have masters you can only send it, that's not the problem. the problem is will your institute be recognized. again search the forums first and good luck!