The .750 gas block at the link below should work with the UTG Pro M-LOK M&P10 Super Slim Free Float Handguard.
https://www.opticsplanet.com/aero-precision-aprh101205c-low-profile-gas-block-750-ar15-ar-308-black-nitride.html
The UTG Pro M-LOK M&P10 Super Slim Free Float Handguard comes with a barrel nut.
The UTG Pro M-LOK M&P10 Super Slim Free Float Handguard should work fine with an Aero Precision M5 upper and heavy barrel.
The UTG Pro M-LOK M&P10 Super Slim Free Float Handguard does not come with a low profile gas block.
Yes, the UTG Pro M-LOK M&P10 Super Slim Free Float Handguard should work fine with a Diamondback DB10. The UTG Pro M-LOK M&P10 Super Slim Free Float Handguard is compatible with DPMS LR308 pattern AR10's.
Yes, this UTG Pro M-LOK M&P10 Super Slim Free Float Handguard will work with a PSA AR10.
There will be tons of options depending on your preferences and the specifics of the barrel that is installed in your M&P-10. Please email us at techsales@opticsplanet.com with any preferences and the exact specifics regarding your barrel (gas block diameter for the barrel).
Yes this will work with the PSA AR-10.
Compatible with S&W M&P10, DPMS Low Profile LR-308 and Variants Using the Same Dimensions
That should be all you need.