Yes, I see the key changes. Just a personal opinion, they occur too seldom, and they are some of the changes used most frequently when modulating music (at least I do, don't know about others), full step ups and downs, and fourths up and down. There may be exceptions that I missed but thats generally what I came up with.
The original theme is the one you had in the beginning, and I know you come back to it, but it doesn't have to be too similar, you could start off with the same interval and trail off into something else, keeping the original feeling though. Sorry if that wasn't clear the first time. What software did you compose this in? If its anything compatible to my archaic finale 2006 I'll see if I can add things to this piece to show you what I mean. Only I'm leaving to the US soon so I might not have time to edit it until I come back.
I think the middle piano section is fine, if shortened a little bit. I'd like to see someone play that interval at measure 169 :P
Looks like this piece is going to yield you a lot good in the long run :)