Some of the big questions I have are
1. How long was Hank Pym Ant-Man?
2. Why did Pym stop being Ant-Man?
3. Why is there no mention of Pym and his Particles in the MCU previously?
4. Who are the villains?
5. How many Ant-Man suits will there be?
6. If Janet is in the movie what is her relationship with Pym and Lang if there is one?
7. Who are the villains and what is there plan?
8. What exactly is the heist for and where is it taking place?
9. What will happen to Pym at the end of the film after he passes the Ant-Man mantle to Lang?
10. Will any other Marvel heroes or McGuffins make an appearance?
some modest attempts at answering them (or at least making my own wishes known).
1. Cold War era secret agent - I'm going to guess at a decade long career ended abruptly by a nervous breakdown; triggered by the murder of his wife
2. I'm betting that Maria's death leads to a crisis of confidence - she may have even been murdered as retaliation for something he did as a government operative - maybe, against his better wishes she came along with him on one of his missions; them being vacationing newly-weds as a cover story
3. his activities were classified & Pym went into seclusion; Jan basically serving as a link to the outside world
4. Castillo - White Power Dave - beyond that, your guess is as good as mine; probably Elias Starr-in-name-only or some hybrid of the Cross brothers - Corey Stoll or Patrick Wilson will serve as Castillo's American liason; overseeing whatever their operation is from the other side
5. two (classic ant-man and the newer model that gets stolen) - and probably a prototype of the Wasp suit
6. estranged daughter or ward of Pym - initial antagonist to/chaperone of Scott Lang but softening on him towards the end; eventual crime fighting partner
7. Castillo's regime is funded, at least in part, by criminal enterprise; drug smuggling, arms dealing, sex trade, and/or organ harvesting. perhaps one of Pym's inventions would increase the efficiency of this operation. Pym particles are certainly useful in smuggling. Castillo would be aware of their function through a past encounter w/ Pym. I'm also almost certain that Castillo had a personal hand in Maria's death. if "Egghead" is actually present, he did gain notoriety for selling nuclear secrets to the commies. maybe something similar will be the target.
8. Lang is identified as a potential pawn in prison. Castillo's contacts leverage him into stealing one of Pym's inventions (or a sample of Pym particles); from a seemingly abandoned but well-guarded lab. when he succeeds at this, they get it in their heads to aim for larger targets.
9. he plays the same role as Bruce Wayne in Batman Beyond.
10. not unless it happens post-credits. S.H.I.E.L.D is defunct. so I doubt Fury or Coulson are going to show up. I could maybe see Lang showing up at Stark Industries for an interview, though. the guest-star would be the Stark logo in that particular case. or maybe Pym would have a meeting with Selvig.