I don't think turning over soil or dig in D.E will help. I used to live in z6 and I had svb on my squash though soil was very healthy and firtil. In your climat you should try to grow earliest squash you can find like papaya or eight ball something that you can havest before svbs are in full swing. Hope this helps.

There are lots of SVB larvae in the top 2 inches of your soil where the squash were, they will emerge next year and attack the nearest squash (yours). Vigorous and deep tilling will directly kill some of them, bury others too deep to emerge, and expose some to predators on the surface.

i read in an old book by Peter Chan that when the wind blows, the base of the stem gets rocked, and an opening is formed in the soil. The stem is then vulnerable to these borers. After a windy day, he suggests pushing the soil back in.

I threw a halloween pumpkin in my backyard last year, the vines are now huge, but no sign of borers. I can't comment on his technique since I haven't tried it, but I think variety makes a difference too.