Best way to rise to the top is maxing your skills first. Since energy drinks are dirt cheap during the first rank, it's best to be too exhausted for games than to work on skills when energy drinks cost 3-4 games salary.
Is it just me or is there a bug involving the deactivation of the weapons' power? If you have a couple defense structures out and actively destroying creep, it seems you can get rid of your deficit by constantly clicking on the red orb on your main structure.
My only complaint about this game are the powerups/money hiding some bullets. Makes me QQ during the final bonus round when I'm on a roll only to get hit by a bullet I couldn't see.
Your recent tweaks made survival too easy. I think all you really needed to do was give back 100% of your buy value. The cheesification was a little too much in the past but only because the creeps didn't drop souls.