Replanting some grass and some alfalfa

I have several questions that kinda flow together. One is I have about 4 acres on the outside of a pivot that either didn't get seeded or didn't come in at all last year. Going to reseed this year after checking soil and doing any amendments necessary. Matching the existing stand which is Timothy, Wheatgrasses, and Orchard primarily, what do you all recommend for pounds per acre drilled? I'm using an old Dearborn Peoria 8' single disk opener which isn't new or pretty but works so I figured a light disc and drag harrow would prep the seed bed good enough, anything else you'd recommend?

There is also about 5 acres at the end of this pivot that I want to rotate from gopher mounds, weeds, and grass to alfalfa. I only have a 16' chisel set up with twisted points, a 12' disc, and a 12' drag harrow for tillage equipment. My thoughts are hit it with those in that order while doing any soil amendments necessary. What ph and NPK values should I target? Also thinking I should wait a couple weeks for weeds to start and spray with glyphosate then seed. Any thoughts on easier/better ways to do all this or specific tips, tricks, and information for each step? Would it be best to plant straight alfalfa or a grass/alfalfa mix and if so what ratio mix and at how many pounds per acre?