Unfortunately, these types of issues can become a process of elimination instead of just targeting the exact issue immediately.
The Fuel System I would start at the beginning: Fuse and Fuel pump relay (which I think you took care of just the fuse?). Fuel pump; Is it starting to fail? Sometimes they die slowly rather than just quitting all together. Is there an obstruction in the tank that is able to shift and block the fuel suction at the base of the Sending Unit (the internal screen filter in the tank can fall apart)? Fuel filter; has it been changed? Same issue with obstruction from debris can block the fuel delivery. Fuel regulator; is it leaking fuel and do you smell gas at times? Fuel pressure; Is it normal? Fuel Injectors; they need firing signals from sensors. Are you getting any codes if checked to a code reader (AutoZone and places can do this for free even with NO check engine light on). And last but for me I would check first; Electrical wiring and grounds. Make sure there's no loose wires or a ground that is broken or failed. I know its a list but it seems to be me if all these items are reviewed you may be able to solve the issue.