We tried to replace a leaky grey water tank valve on our 2000 Chinook Premier, but the screws/bolts were so rusted on, we had trouble getting them out and in that process broke two of the loops on the flange/spigot/whatever that holds one of the screw in place.... So even though we replaced the valve, one of the four screws couldn't be used because there was nothing to hold it in place. So it's still leaking slightly. Any creative ideas how to fix this or do I have to cut the pipes and replace the flange/spigot things that hold the valve in place? I'm a little nervous about cutting the pipes and I don't currently own tools to do that... If I was a normal person, I wouldn't mind building up a tool collection, but.... We live in our Chinook so not much tool storage space. Thank you!
I am not sure how bad that is but I have had good success repairing ABS with a slurry made by dissolving ABS pieces (old ABS pipe cut into pieces) in Acetone. I keep a Mason jar of "slurry" around just for these type of repairs. I use a very thin slurry as an adhesive to bond broken pieces and a thicker slurry for more substantial repairs. As always YMMV.
You can look some videos up on youtube. (That's where I got it from)
So even though we replaced the valve, one of the four screws couldn't be used because there was nothing to hold it in place. So it's still leaking slightly. Any creative ideas how to fix this or do I have to cut the pipes and replace the flange/spigot things that hold the valve in place? I'm a little nervous about cutting the pipes and I don't currently own tools to do that... If I was a normal person, I wouldn't mind building up a tool collection, but.... We live in our Chinook so not much tool storage space. 
Thank you!