Confused about tmx & xtol in trays

[mikeb_z5]

I'm new to developing my own film so please take pity on me

Last night I developed my first 4x5 tmx negs in 8x10 trays using Kodaks constant agitation method and 1 liter xtol undiluted for 6 3/4 min @ 68F. no problem there. the negs look ok and contact sheet looks good so far. The scene was what I think to be of normal contrast.

My questions are as follows:

1. why undiluted in trays?

2. I have some low contrast scenes that I think require N+1 and N+2 development. the tmx data sheet says to refer to the xtol data sheet for development times. but the xtol sheet does not have any contrast adjustment table. the tmx does. Do I use the tmx table with the xtol development times?

3. Am I correct in thinking N+1 is about a 40% increase in dev time and as starting point? N+2 an 80% increase?(Am I nuts to be trying this N+/- stuff right off the bat?)

4. I have read here and elsewhere that xtol 1:1 or 1:2 provides greater sharpness. what does this do to my development times?

Thanks for your help. I hope I don't sound like a complete idiot

Mike