This stuff you linked to is NOT economical. It will run you just about $150/acre. Comes to $750-$900, yes? That’s a BUNCH of money you don’t have to spend.
For your acreage go to you local co-op and get 2.5 gal. of 2,4,d Ester (if you are going to spray within the next 30 days; if it will be longer then get 2,4,d amine; the general rule is “ester before Easter” as it works better in slightly cooler weather). In our co-op it will run about $60 and you’ll need a gallon or two of surfactant (a soapy substance that causes the chemical to better adhere to the weed’s leaves which means a faster and more complete kill; figure $12/gal.). You will likely have to spray twice, once in the spring for early emergence weeds and once in early summer for the late emergence weeds). The coop will usually give you advice on use.
I’ve been doing a LOT of research on liquid fertilizers for pastures and it is a subject that is VERY controversial with some farm folks. I’ve not yet made a final decision on liquid or dry bulk. For your rather small acreage you might be better off with bagged fertilizer and pull-behind spreader for your 4 wheeler. First, however, you need to do a soil test and decide what fertilizer you need and if you need lime. Contact your county extension office for advice on how to do this where you live.
It’s possible to bring a pasture into decent condition over a couple of seasons with just using fertilizer, lime (if required), and weed killer. If you decide not to use 2,4,d (a very same chemical that has been in use for decades) then close mowing will help, but plan on a multi-year program and lots of time on mower.
If you want to do this right you need to soil sample, RoundUp, reseed, and the add the right mix of fertilizer and lime. You might be able to graze in the Fall but will have a really good start and a strong stand next spring. You might have to hit it with 2,4,d as you soil will have seed in it that will take a couple of years to fully “clear out.” As to grass type, talk to your County Agent for what works in your area.
Good luck with your program. 
G.