I got $167,636+$1500 mission bonus from a 19:31 duration flight, then I unlocked 5 other missions from that flight. At that time I had lvl3 rocket parts.
The trick is to keep shutting off the thrusters while in space to keep drifting. By doing that I was able to get more fuel from pickups than the fuel I used. My fuel-saving upgrade was only lvl3. Also make sure that you collect nearly every fuel pickup you see, especially in space and the outer atmosphere.
I won't bother with the last achievement for now...