The capacitors on the mosfet drivers are the wrong way round. The bootstrap cap must be much
smaller than the decoupling cap or you'll crowbar the supply on every cycle.
33nF is probably fine for the bootstrap, 1 to 10uF for the decoupling cap, both must be ceramic.
If the MOSFET has a total gate charge of N nC, then a bootstrap cap of N nF will be sufficient
(it will only droop 1V). 33nF will handle most MOSFETs fine. Its good practice to add about
10 ohms in series with the bootstrap diodes to reduce noise injection on the 12V supply rail.
The diodes across the output connectors do nothing, the bridge provides full free-wheel diode compliment
as you use MOSFETs with body diodes.
If you have 12V MOSFET supply then you need to condition it before presenting it to the
MOSFET drivers - the main supply rail will be very noisy and MOSFET drivers need a pretty clean
12V. (Instant catastrophic failure can occur due to spikes on the 12V, note, I've been there)
You need some heavy duty decoupling on the supply to the MOSFETs, lots of electrolytic and some
ceramic is good. You have none.