How did Captain America survive so long in the ice and why doesn't he age?

[tg1982]

So when they say that all of the SSS has been removed from Steve's system, are they saying that something was introduced into his system to counteract and reverse the changes to his DNA?

They're really vague in regards to that. All that's been said, in book, is that the SSS is completely gone from his system. I would like to point out , the exact same thing was said when he had it drained after the "Streets of Poison" arc and also in the "Operation Rebirth" arc. Both times it was shown and stated his body could replenish it and during his SSS-less state he did not age.

Most likely they are keeping it vague for an easy explanation for when Steve inevitably get the SSS back, de-ages, and becomes Captain America again. Probably in time for Captain America: Civil War. Though that's not an absolute.

It's gone. Whatever the process that changed his genes from sick, frail weak human being, into, strong healthy smart super soldier, has been reversed. He is now back to the genes of the sickly human being. Trouble is, he still has the muscle memory of the Super Soldier, because he can still hold his own as Commander Rogers.

I'd be really surprised and impressed if, when Steve goes back to status quo, they simply say his body replenished it, like it's been stated and shown in cannon. Or if they'll concoct some unnecessarily elaborate and pointless storyline of him needing to get it back. They'll probably do the later though.