Thanks for clearing up those doubts. Just a suggestion with the surround cards, you could pretend the 4x4 grid is an island surrounded by water. Therefore when a card with surround is adjacent to a space off the board it counts as if it's surrounded by 1 card. However this may require buffing the stats/abilties of the surround cards, so as you said there really isn't an elegant way to add an exception.
Yes, I did play the game. I printed out the cards first in black and white to test them out. I used the first example deck and printed two copies of it. I played with my younger brother who is 12 years old, and he really enjoyed it so in terms of age groups, I definitely think this is suitable for 12+
A cool combo my bro did was he placed Dr. Steel to resurrect one man army. Then he used return trip to return Dr. Steel to his hand. Then he placed Dr. Steel again to resurrect a second one man army, leaving me helpless. So combos are a big part of this game.
It's a shame that you haven't found many playtesters because the idea is really unique and something I haven't seen before. It's also quite balanced and fun in terms of mechanics.