Game size after export is 46MB.
Memory use in game is 429MB
In C2 estimated Memory use is 509MB
CPU util in debug is 14%
Windows 7 SP1 64Bit
Quad Core I5 processor
14% CPU use from an i5 is fine for mobiles. It's exactly what I get for Star Nomad during combat. Runs very well even on pretty weak stuff. So whatever is the problem, its NOT on the logic side of things.
500MB is not going to happen for iOS, no way, no how. Its also extremely on the edge for a lot of Android devices. If they even run your game at all, once they go to the homescreen and it suspends, they cannot resume due to overloaded memory, your game will crash & restart.
At this point I suggest you really reduce the resolution of your images, theres absolutely zero need for them to be high res. What looks awful pixellated on your PC screen looks perfectly acceptable on a small device of 4-7 inches.
Cram everything down into power of 2 sizes, 128 x 128, 256 x 256, 512, 1024, etc. Do not have images that are a bit larger than power of 2 size, its a total waste of memory.
For example, a 557 x 600 image uses 4MB in memory. But a 512 x 512 uses 1MB only. Likewise, if you have any image thats even a tiny bit larger than 1024, its 16MB in memory for that single image.
ps. I made the same mistake as you with my first big game (mine was 460MB in memory on Android hehe), make it first then optimize later... completely stupid way to do games, especially for mobiles. I learnt the hard way.