Seeing as there are quite a few people getting past wave 20, Sikes, then obviously the issue lies not with the game, but something you are doing (or not doing).
I don't think fame has anything to do with claiming titles, unless there's some other way of obtaining it rather than through searching the town.
You get new titles simply based on the level, I believe.
If you're stuck on the survival waves, try to stay away from the center of the screen (vertically) that way you'll only have 3/4 sides shooting at you at a time.
I've made it to 69 (on easy), using nothing but blade shooters, cannons, pineapples (extremely useful against large groups of units that come out of the MoaBs), and 1 monkey beacon in order to increase firing rate.
Once you go into free play you get around 1/3 as much money as you should from your kills. Is this a glitch or intentional? Either way, I think it should be changed so that you continue to get 1 money per balloon popped.
I suggest getting nothing but orange until it's maxed out, nothing but cyan until it's maxed out, then nothing but purple until it's maxed out. After orange is maxed put all points on red.
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