I have no experience with the Dynavin. However, it sounds strange that the BT info does not come through the front RCAs. You may want to check if the HU is configured properly. The GPS announcements are likely in mono so the processor sends them to the center. If they are not loud enough you may also check the settings on the Dynavin. You should not have to crank the center just to hear the GPS info, which surely will have a negative impact when listening to music.
Edit: The amp getting hot is quite normal. On a sunny summer day I can barely touch my amps (JL HD600/4 & Kenwood XR-4S)
Mobridge DA2 > JBL MS-8 > JL Audio HD600/4 > (3) Hybrid Audio L3SE & (2) Rainbow Cal25; JL Audio HD900/5 > (2) Morel HCW-10 & (1) AE SBP15