Yes it is for a .750 gas journal.
The ODIN Works Low Profile Gas Block model MPN:GB-ALUM measures 1.9" in length.
Yes, the ODIN Works Low Profile Gas Block is compatible with barrels that feature a 0.750" gas journal diameter.
ODIN Works does not state the exact reason why the ODIN Works Low Profile Gas Blocks are not compatible with pistol length gas systems. It is probably do to the pressures as the gas system. I recommend contacting ODIN Works for that information.
Yes, the .750" will fit your barrel.
Yes, this gas block should fit in that handguard. There likely won't be much excess space though.
If the one you are commenting on is this ODW-RGB-OWLPGB-GB-75 carbon steel model, it will still use the 7/64" wrench. Only the stainless uses a different size, and that model ships with the proper sized wrench.
You will need the mil-spec at minimum. Max operational weight will unfortunately depend on the barrel's gas port diameter and length between the gas port and the end of the barrel.
The dimensions of the adjustable model can be found here:
https://www.odinworks.com/v/vspfiles/assets/images/adj%20gas%20block%20measurements.jpg
The non-adjustable models dimensions are not provided, but you can use the adjustable gas block dimensions to gauge compatibility as it is taller and wider than the standard gas blocks offered by Odin Works.
Yes, it does.