There is a little lack of participation on these boards. I have owned both a Dosmatic and an EZ Flo Fertilizer injector. Both are good but ...
Dosmatic - Water driven pump. It is load, but accurate. Did I mention it is noisy? Since it has moving parts, it will require periodic maintenance. It is also recommended that it be cleaned out after every use by running 1 gallon of water through the pump. The size of the fertilizer container is whatever size you want it.
EZ Flo - No moving parts. Less control over the injection ratios (no bid deal though). Minimal maintenence, if any. Captured fertilizer container, but the unit is quiet. For such a large size lawn, I would recommend the high capacity units.
Fertilizer - Find a lesco store near you. Hopefully you have one. I use thier MaronN sprayable fertlizer (20-20-20). It is about 37 dollars for 25 pounds. My 9.5 gallon EZ-Flo takes 50 pounds of fertilizer.
Instect Control - I use a Pymethrum (spelling?) product from Lesco. It is toxic to insects and fish.
Soil development - I also add kelp (i.e. seeweed) plant food in liquid form. About 1 gallon per cycle.
You can add other things also, but you have to be careful of the chemicals interacting with each other. Post more questions as you get them.