1) Mid to late summer is generally the best time to spray in a situation such as yours. I would mow first and let the weeds regenerate and then "nuke em"

2) If done correctly, one application will kill the majority of the weeds and grasses, new seedlings will sprout but they can be controlled easily with tillage. I would use a 41% Glyphosate @ 2 quarts an acre if its mainly grass. If its lots of broadleaf weeds, then I would use 1qt of gly + 1 pint of 2,4-D amine per acre. In 1 to 2 weeks the weeds/grass will be dead.

3) I apply fertilizer right before planting, especially nitrogen.

4) Lime works best if applied 6 months to 1 year in advance of planting, depending on what is being planted.

5) If help is needed identifying the type of weed or weeds, we could help if you had a picture.

Depending on a soil test and what is being planted, will determine what type of fertilizer and the rate. The soil test will save you money.