Firstly, I wouldn't bother with the I-129F once the I-130 has been filed - K3 visas are taking, on average, longer than immigrant visas.
As for your questions:
1. Yes.
2. Yes, provided all your paperwork is in order and your case is straightforward.
3. Shouldn't be a problem but you will need a US address also. You will still have to file through a service centre in the US.
4. Not that I've heard.