you tap the line at the closest point on the MAIN line. don't tap inside the house, find the main pipe coming from teh well, cut it and glue in a TEE if it is pvc, solder in one if it is copper pipe. from teh sound of it, you may just want to hire a plumber to run teh main connection.

as far as increasing pressure/flow, if your well can only provide the above listed volume then you may be SOL. the best way to test a well is at the closest spigot to teh pump. usually there is a boiler drain at the pressure tank. of course, it should also have a guage on the tank! if your well supports it, you can adjust/replace the pressure switch to get a higher pressure. the limiting factor is how much water your well can produce.

my well produces a constant 65PSI and can fill a 55 gallon drum in under a minute. my dads old well did good to hit 40PSI and took 5 minutes to fill a regular bathtub.

it sounds like you will need to get a pump relay switch Hunter or Rain Bird make one. This will keep your pump running the whole time that your irrigation timer is on, and will keep your pump from burning out.

Here is a link that might be useful: do_it_your_self_site