My first suggestion would be to run it thru corn for a year.  But I see corn is not an option.

My question is:  are those tolerant broadleaf weeds up and growing yet?  (Technically, they are tolerant, not resistant - there is a difference ;)  .)

I would probably max out the Powermax rate, and add 1 pint 2,4-D.  I don't like to use any more 2,4-D than I absolutely have to, ahead of seeding grass,  and I'd really prefer using no 2,4-D at all ahead of seeding grass. 

If you are seeding grass, you may just have to do the best you can right now, and look at broadleaf control once the grass is well established ( i.e. this fall).

That is my assessment.