The fuel pump should be attached with two bolts. Once the lines are free, the pump should be able to be dislodged once the bolts are removed, then brought down and out.

A bolt and nut generally means that the original bolt was dropped and lost, and a longer bolt put in that was too long for the job, so the nut was used to tighten down the pump. Back off the nut first.

If the bolts are stripped, you can use the pump to attempt to influence the bolts outward while ratcheting them out, you may be able to grab good threads to back out the bolt. As it comes away from the block, an oak 1x2 is my favorite tool for persuading objects to back out without damaging them.