1.1 - Yes. A small edit on p. 171 of SO is required: "Vacuum or Tainted Atmosphere (due to bulky suits)" CHANGE TO: "Vacuum, Tainted Atmosphere or Submerged (due to bulky suits)"
1.2 - Yes
2.1 - No. You'd have to land on the submarine, then go below.
2.2 - Yes. It's basically a well deck situation. One assumes the sub designers would be clever enough to know about that.
2.3 - Yes, provided the submarine is no more than one level above the unit being recovered. The Wyrm SDS Submersible Fortress has them.
2.4 - No
2.5 - Yes