So just how much of the practice schedule should you use a metronome for.?

The metronome is perfect, it is never ahead or behind the beat. It makes sense to play along with it rather than trying to keep time yourself because we human beings are not perfect...but the metronome is ;).

There are lots of good free apps for metronomes, that's what I use. Also, good free tuners and chord charts, all free.

Yes. There is a nice one on the iphone in the app store called "metronome" by "steinway & sons." I use it daily. Makes a nice clicking sound. I don't care for the ones that go beep beep beep beep. Good luck!