I am the physician in question 3. Once I've completed my intia requirements, can I independently read both screen-film and FFDM examinations?

No. 

Because your initial training was only in screen-film, under MQSA you are qualified to read only screen-film examinations independently. In order to read FFDM examinations, you will need to obtain and document eight hours of training in FFDM.900.12(a)(1)(ii)(C).