We had to tear up the floor. There was water damage from years of leaks. Tabitha counted eight layers of flooring. The worst was the upper most layer of particle board. It was nasty, spongy and nailed with far too many ring shank nails.
I plumbed new gas line to where Merrick the stove will live. It is flexible stainless steel line. I had to get certified to install it but it is great.
The new subfloor really changed how sturdy things felt.
I used a heavy duty ratchet strap to jack up an inferiorly supported joist. Going into the crawl space is an event and must be avoided if possible.