Interesting! Just yesterday I took a test exposure with an Elioflex_2 (transferred the 120 film mid-roll from another camera...) and developed it. Looks alright, did not enlarge or s**n yet. I'm curious how you even got so deep in dis-assembly to lose the shutter release button: I intended to clean the shutter (slowish) but gave up; all I did was clean and re-lube (with teflon grease) the focus helicoid.
What type of film would you recommend? I think I would like to try colour film for it first. Later BW.
With an MF camera, don't think twice: use 400 iso film. Ilford XP2 if you want to try BW but don't want to develop yourself. The extra grain (if any) is more than compensated by the larger negative. And, being able to shut down the diaphragm a stop or two helps with a triplet lens. And all negative films like over-exposure better than under-exposure. Speaking of triplet, it's possibly better than you think; if you want to evaluate its real potential, shoot with the camera on a tripod.
As concerns focus calibration. The easiest method IMO is that proposed by Rick Oleson:
http://rick_oleson.tripod.com/index-123.html. Except in his description, bot cameras are SLRs. In your case, I would put the ground glass (or even clear glass with a sharp pattern) on the back of the elioflex, and use a known good SLR to check for infinity; the principle is that when both cameras are at infinity, the pattern appears in focus viewing through the combined optics.
I would not consider the camera lost. Be creative. For instance, obtain from someone else a good face-on picture of the focus ring, hopefully metric scale (I would be willing to do that, except I'm not sure the eiloflex2 has the same optical formula, the max aperture is slightly larger). Go to a printing shop and have it printed on a plastic substrate, overlay with transparent foil for protection. Once you have infinity calibration, just glue your scale on top of the lens ring. As concerns the shutter release; Look around. Maybe the button of a retractable ball point pen will fit? Or, use a shutter button from a different camera model, with the threaded hole: fix permanently and you'll have to use a flexible release (not a bad thing).