Problem with rear rim (oldish bike)
 

It is a Raleigh Capri 1983, I have the bike on it's back as I do not have a good bike mechanic stand.

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Alright so I'm hoping the pictures aren't too blurry and that I'll be able to explain this well enough. But my problem is basically where I'm supposed to tighten the nuts in to keep the tire in place. Everytime I begin to tighten it the tire starts to move forward and tilting to one side as the last picture shows. The rear derailleur (first picture) is what is holding that side from moving back too much, now on the opposite side there's nothing there to keep it from moving, and as you may have noticed there's quite a bit of space at the end of it.

You guys might have noticed that the screw on the side with no derailleur is sticking out a bit more, I figured maybe that was the problem so I bought some washers to keep both sides even and hopefully keep that side still. But no. I can manage to get the tire in the right spot, but that would mean I'm not tightening the nuts nearly as well and once I get on it and hit a slight bump it just shoots out of place. Can anyone help me out with this? Maybe if you own or have owned the bike in the past?

Again, sorry about the picture quality, camera kept focusing on all the wrong this. Appreciate the help!

Hold the tire in place(centered) with a piece of wood, or a wrench or something. Jamb it in between the chainstay and the tire while you are tightening the nuts. Alternate sides, tightening a little bit on one side, and then on the other. Don't worry about one side sticking out more than the other, as long as the short side has enough threads to allow the axle to go completely through it. Take the washers out; you don't need them. Tighten it down good and tight, and see how it goes. Try some nuts with a lock washer built in. That should do the trick.
I have worked on many a bike in the upside down mode. Nothing wrong with that. Good luck.

1- make sure the derailleur mounting plate is fully back in the right dropout and tight.
2- install wheel all the way back into the mounting plate, and hold it centered between the chain stays with one hand while tightening the right bolt firm, but not necessarily full tight.
3- at this point the wheel should stay close to center on the chainstay if you let go. If it moves way off center that indicates that the dropouts aren't parallel and is something you might to let a pro take care of for you.
4- holding the wheel centered tighten the left nut, then tighten the right full tight.
5= go ride it.