Looking good! From your pics, I can't really tell where you welded, but I put 2 upside down L brackets under the winch plate and welded them to the either end of the end of the frame, and then to the bottom of the winch plate. In your picture, where the 2 little circles are located at the end of the square frame tubing in your pic below.
Additionally, for the rusty bolts, I'd highly recommend https://www.amazon.com/Boeshield-Rus...dp/B000FVWA66/ and
https://www.amazon.com/BOESHIELD-Cor...dp/B0002Q9F26/ They both come in a variety of sizes.