Broken bolt slide in Model 30

Help! I have an old 12ga. Hiawatha model 130VR which is the same as the Savage model 30 from about 1960 vintage (it was my dad's). About 10 years ago I had the bolt jam in the shut position after firing. The gunsmith said the slide had cracked (which he said was common on some Savage models) and rewelded it. The next time out, it did it again and I let it set for these 10 years, until today. After I finally got the bolt back and out, I saw that the idiot couldn't weld (I'm in the steel business, so I know these things). Now after seeing several slides for sale on line, it seems that there are quite a few variations of the model 30 bolts & slides.
My gun has NO serial number anywhere that I can find??
I guess that I can have my shop reweld it properly and flatten it, or continue to try to find a slide that appears close to mine. Even after fixing the slide, there is still the question of why the bolt was not locked to prevent the kick-back??
The gun still has excellent blue and hopefully can be made whole again.

I can date it if you can find the date code on it, it'll be a small circle with a number and a letter stamped inside of it.

Sometimes with those Savage pump guns you really have to rack the slide forward to make it lock. I had a 170 in 30-30 that was the same way.