Calm down there boy I say. I say calm down.

It sounds like you have a Whitworth Express. this was made by Zastava in the old Yugoslavia. It is not a CZ/BRNO. Whitworths are very nice rifles and normally shoot extremely well right from the box. I don't know about the bedding and recoil work but that rifle is probably capable of much better than a 4" group.

They were shipped to England for final fit an finish and are in every way superior to a CZ. It is too bad it was home smithed but you will be alright.

That rifle needs a front recoil lug, despite what your smith tells you. Have one put on and bed the action and the first few inches of the barrel. Free float the rest.
I don't know why a new screw wouldn't tighten up the express site. Add some locktite

Replace the trigger assembly with a Timney with the built in safety, or better yet, put in a Timney and a 2 or 3 position Winchester type wing safety.

You can replace the very hard recoil pad if you think they make a difference. (I don't)

I like the Whitworths allot. They have the feel of an English rifle and are light and very handy.

Anything under $700.00 is a good deal.

Forget about screwing around with other cartridges. Just load it down if you want.