Mix them with feed oats. Use feed oats as a nurse crop many times. Cant say much about weeds, but never seen a bad breakout of anything. Some weeds are just a part of doing things.
double tree drill bit size? I use a solo 421 spreader. It has a prouble opening window. 3/64 - 1/8th would be my guess. IF I can find a replacement wndow opener, I would just drill a hole in the window. Use lime or fertilizer it won't matter if its there or not. Drive over a blacktop driveway, a big tarp or snow while spreading seed at a reasonable speed and known pto rpm. Get how wide the spread is.
Now park the spreader or a certain opening in one spot, catch all the seed with a tarp. Either put a known amount in and time it, or run some for a few minutes and then weight.
5mph * 5280ft/mile / 60 minutes in an hour = 440 ft per minute. Assuming a 16ft wide path. 16 * 440 / 43500 ft^2 an acre = .16 acres per minute
IT take 7 minutes to dump out 20 lbs. 20 / 7 = 2.86 lbs / minute. 2.86 lbs per minute / .16 acre minute = 17.8 pounds per acre.
Keep in mind your rate control is often at the operator end of the cable. Open and close it, the opening can vary from time to time. Small changes in the opening can hange alot of straight clover flow.
Get the opening right where you want it, leave it alone. Use a piece of plastic to cover the opening, tie a string to it. Yank it out when ready.
Clover is a tough one to do by itself, even with ideal styles of spreaders. Your getting a ball park figure. Expect to use more. Leftover clover stored well will be fine next year. Very often bacteria coat is really not needed. Seed itself will be about the same quality on year 2.
What works for one clover seed will be different with another. medium red is bigger than whte clover seeds. crimson is even bigger than medium red. The amount of coating varies too.
Spring clover and oats are awesome. Oats dont frost seed though.
commercial or larger retail nurseries use seeds hulls for mulching. I have heard of sand being used. Fertilizer mixed with clover comes out just fine too.
I had a broabcaster pto spreader, I would probably do 2-3 parts lime, 2 part 6-24-24 or just potash 0-0-56 and clover, then tune as above with clover. Clvoer and oats just eat up the potassium. A little borax soap like 4lbs / acre will add some boron int here too. turnips and clovers love that stuff