I'm not sure i'm understanding you properly, how is your AGND actually grounded if it doesn't connect to the regulator ground or the battery negative in attempt to not connect it to the DGND?
What are you amplifying the output through? I would imagine you might have problems connecting it to external devices, but if it works then it works i guess.
The way i read it you should connect the ground on any digital stuff to the DGND to prevent it introducing noise onto the analogue ground. If you haven't got any other digital stuff then i don't suppose separating the grounds matters that much.
utsource will sell you PT2395's for about $8 each, but i think you need to buy a RAM chip as well
http://www.utsource.net/