Fuel sending unit

[mieth]

Sorry this is so long, but I'd really appreciate your opinions.
1989 Jeep Cherokee, 4.0L, 20 gallon gas tank.
Starts difficult and has poor acclereation.
I recently replaced the fuel pump on my Jeep and noticed that the fuel sending unit had some broken welds on it. The Fuel line (which also mounts the fuel pump) was loose and wobbly. I replaced the fuel pump anyway and reinstalled the damaged fuel sending unit because I couldn't find a replacement that day. The Jeep ran really well for about 55 miles, then started having acceleration problems again (that's why I replaced the pump in the first place). Now I've got three questions:
1) There is a second line coming out of the sending unit cap, I think maybe a vent or something like that. With the broken condition, it might be pressed flat against tank bottom. Could that be the cause of the original acceleration/hard starting problem?
2) The negative terminal of the fuel pump is grounded to this same loose tube. Do you think it's possible that the fuel pump is cutting out due to the less-than-perfect ground?
3) A new sending unit is about $200. Is it possible to have the sending unit repaired by rewelding? If not, does anyone know of a place I can get a replacement that won't cost an arm and a leg? Local junkyards do not have this part.
Any and all comments are welcomed.