Now that Nuremberg Codes is finished, probably going to add some chapter updates (and may post a poll) to other fics. The sequel (temp named Aftermath), is already planned and outlined, just needs the actual writing. But I do get to share some things about Nuremberg. I'm happy to answer questions as well.
Ghost/G-09's coping mechanism was to somewhat ignore what was happening. In some ways dehumanizing himself to cope.
There's no supernatural reason for Colt appearing in Price's nightmares. It's simply a decision he feels guilty about and over time became an amalgamation of regret over past choices, personal fears, and the weight of the position he's in. In some ways having those nightmares also kept him sane. But these nightmares in some ways separated Colt from Simon.
Yes, the Riley's are still alive. Except for Brian Riley, he died due to cancer/long term damage of internal organs due to alcohol and drug abuse. As far as they know, Simon died in the mission to Mexico.
There were other experiments, including animal experiments (running under Greek alphabet batches). The A-J we see is simply one group.
Gaz being the reason they escaped is because he deserves it.