HIYA! I didn't notice the location in the first post....
We may have passed each other on the roads here over the years I've been riding.
The good news for your conversion is that any freehub body and center screw combo will fit onto any Shimano hub so if you can find the hub you want and another with the old school IG or HG 7 speed freehub you can mix and match stuff to put the spool with the right spoke count with the shorter freehub.
Yes jamming the wheel in will spread the stays but my fear would be that it wasn't squished evenly but rather it was bent more on one side so the wheel would be sitting off center. I'd rather jig up and measure it and then cold set the offending side using the information at Sheldon's site to restore and correct the spacing and offsets of the stays to the proper settings.
Being an '83 I'd say it would have used either a 5 or 6 speed freewheel setup so if you want to get a 7 speed freehub setup in there then just keep on tweaking and measuring. But there's some offset to consider. The drive side needs to be tweaked out a little further on the new wider wheel setups. I'd have to check to see if this is the case on 7 speed bikes. Certainly on the older 5 and 6 speed stuff the wheels are symetrical and the dish is what compensates for the gearing.
Here is all you should need to check it out including a setup using string to check the alignment without using a jig...
http://www.sheldonbrown.com/frame-spacing.html
Once you get it set up be sure to take it to a shop for them to bend and tweak the derrailleur hanger for alignment. After all the tweaking that hanger will definetly be out by a little and mess up the shifting.
For light touring I think you're going way overboard on the spoke concerns. For less than heavy loaded touring 36 spoke lacings and a slightly wider cyclocross style rim with 28 to 34mm tires is going to be just about bomb proof. But check with the guys in the Touring forum for a final on that aspect. Maybe go with butted spokes for the extra resiliency to shock loads they offer.
Sounds like a fun project overall. Just try to keep the Unobtanium items out of it and it should go smoothly.