1999 B3000 Electrical/Fuel??

First time I'm doing this so I hope it ends up in the right place. Mazda B3000 has been having electrical issues (horn honks randomly and wipers come on). Couple weeks ago we thought it ran out of gas but it was the fule relay. Now when you drive it, it jerks and hesitates. The left blinker wouldn't work for a while yesterday. The gas needle stayed at fuel for days, would come down to 1/2 way and then go back up. Mechanic said to run a couple of tanks through it then we could try replacing the fuel filter. Any thoughts, please!!