So I went outside yesterday to check tire pressures , and found this . On a scale of 1-10 how screwed am I.

 

I'd say around a 6-7 because its so tight to the jack rail. The big Q is, how far back in has the corrosion effected the metal being its right where it can wick water and other contaminants back in there.

Personally, this would be my effort barring what is found as you go along.

Orange...cut out with a die grinder, depending on how far the rust is, you may need to cut more.
Yellow...spray the hell of that area after cutting with a rust inhibitor, let sit per instructions. There are many on the market, alias naval jelly.
Green line...make a plate to inset to the flr board bucket and yes, that's a lip for that tuck if you can get a piece made to go in there.
Green squiggles...this can be either of 2 things. A bonding adhesive like DP-1 or product like Solder Bond. I don't know if they make either of those anymore? To prevent this incident again.
Then I would rivet the plate in to secure the bond. Let it dry, then you can put some kind of body putty to make it look good and spray it with some undercoating. Or if you don't care about the finish and just want to call it a day, spray it with undercoating.

My first car was a 73 Nova rust bucket, I was 15. After repairing the rear quarters with aircraft aluminum, I packed the inside corners with roofing tar (had to leave the trunk open for a week for it to stop smelling...lol). I then sprayed the whole bottom kick panel and rear quarters with a thin layer of quick dry undercoating. Then sprayed the car a sweet metallic green. I think I missed my calling because I'm pretty sure I was the first person to undercoat the quarters and color spray on a car?

 

I have it going in on Wednesday for brake pads (and possibly a wheel bearing),and an A/C evacuation and recharge , I've also told the shop to give me an estimate on the rust repair (as I have no idea how to weld and would like to keep the car)

 

bust out the hammer and start sawing any weak metal in the mean time

 

That's why I gave you the instructions I did, no welding involved.

 

Just this spring I welded same spot(at both sides) in my xjr. In my case it wasn't through yet but not so blunt head hammer went straight thorough. I'd say that with that much of a hole you gonna have to make patch to inner sill too. And dig out as much as you can the yellow bodyfiller what factory used quite generously on every sheet metal joint. I had to "grind" it out 4cm upwards the firewall from the bottom left corner at drivers side untill no more rust was underneath it.