Resources indicate how much the OF has to spend on new things or replacing the ones you blew up. You cannot find out how many resources they have currently, but will be able to in future.
Threat will control how much resources the OF is given (multiplied by difficulty level) to be distributed into more soldiers, base upgrades, more vehicles/hardware etc. The OF will receive resources every 6 hrs (same as your taxes + donations) but will be spent hourly on a drifting random schedule (ie not on the hour every hour).
Resources can be spent on:
Each base owned by the OF will manage a “defense” force and a “reserve” force. Prioritizing all incoming resources to the defense force and using any remainder on a reserve force + upgrades. The defense force will be spawned and defend the base, the reserve force will be used for patrols and QRFs.