A buddy that I work for has several sizes of JD’s and Kubotas and bought a new Kubota M7060 with cab a few weeks ago, I used it one full day last week and liked it pretty well for a mid size tractor.
I wouldn’t think it would kill your oats, I have a Woods that is similar to your Firminator and I plant into living plots all the time with no problem.
I wouldn’t mix the clover in your 3 point spreader, use your 3 point for the big seed and spread the clover with a chest mounted/over the shoulder walking spreader.
I was in your shoes for a long time and finally bit the bullet and bought a 7’ Woods minimal till planter about 5 years ago, it has small and large seed boxes and works great. It cut my planting time by about 2/3rds and I get much better germination, my only regret is that I didn’t buy one many...
I’ve been using boomless for a lotta years on my small atv sprayer and would never go to the hassle of booms, now on our 500 gallon pull behind at work, booms are absolutely the way to go but not on a small atv sprayer.