That amp is 1ohm stable, so you shouldn't have any problem. As for your battery question, what are you trying to do? A battery can only hold so much amps. It doesn't take much for the amp to drain it, usually about an hour or less. The voltage is always 12v from the battery.
i think that amp is more for competition. i dont think you can run 17.7v through your battery. it would probably explode lol.
if you have the money for 2 type x's why waste your money on a sh*tty amp like that? and that also will be underpowering those subs. you might wanna try a better amp for around the same price. i think you can get the brutus 2200 for like 300 or so but im not sure. that might be a better idea for you.
they got the high reading from running it at more volts so disregard 3000 watts. it might ptoduce 1500 rms. it could be overrated. im mean they said 3000 watts. but they didnt say the voltage. try getting an amp for each sub. like the orion 1200d or kicker 1250 sx. just keep looking.. just keep looking.. just keep looking... hohohohoho.