If you fly out of MHT, your sole option as between US & AA is to earn on US anyway. So, you might as well obtain your DM# and start using it as you fly.
There is no way of predicting exactly how and what the new AA will match, but it really doesn't matter since you don't have options anyway. While it's unlikely that the new AA will match US Gold to AA Silver, if that happens, you really wouldn't have done anything differently anyway.
It is possible that the new AA will offer some form of match to UA elites as part of the new 3-way tug-o-war with UA & DL, but that's speculation and since you're only UA Gold, that likely won't help much given your intended travel pattern.
Nonetheless, as announcements are made regarding the new program, make a point of reading them carefully (and then reading them again).