Never had issues with crediting, either booked on a DL ticket picking up a codeshare in AMS or LHR or alternately booking directly online at the Aeroflot site. Enter number and voila. E+ benefits have been tough to push for, especially in Russia as they claim that ST rules don't apply - real reason is that they don't want to deal with you if it is additional work.

Interlining should work, but it will depend on the competence at your originating airport. You will likely enjoy on the international portions, but some domestic Russia flights can leave much to be desired. No S7 mind you, but still not great.