Back from archery. Took a few more pics. The rail “clicks” into place and requires a hard pull to “snap” it out. No bonding agent or loctite has been cleaned off and the fitment appears to be pretty tight, with a slight pressure and the gap between rail and barrel closes. I would guess the rail to be correct. You can also see bonding agent used at the front, not just rear. It’s overhanging the dovetail and I was able to lift it with a fingernail. I have not touched any of the bolts or tried to thread any in to the minimal threads that are there. Don’t have anything here to measure holes, caliber died and hasn’t been replaced.
Old fella is off today. I’m going to call tomorrow. Hope for more than a “just drop it off”.
Looking at the photos with the base in place, it appears that the top of the base slopes downhill - higher at the breech end than at the muzzle end. Strikes me that the top of the base should be essentially parallel to the axis of the bore.
You really need to get the thing to a competent smith, at least to analyze the situation, perhaps prescribe a solution, maybe fix it. Personally, the person who did the job initially is not someone I'd want trying to "fix" things.
You give your location as NE ON. Would it be reasonable for you to get it to Jason at Gunco in Nepean?