The fabric IS waterproof, but there is a big hole where you enter/exit that is NOT waterproof.

I had an REI Minimalist years ago but returned it because it was cut a little narrow to allow my 20 degree bag to fully loft.

Match the tool to the job. The Minimalist is a good choice for short alpine trips.

Whoopieslings.com (go here for guy lines specifically, otherwise click on the store from the top of the main page) - you can get a knotless set of guylines with or without the tensioner, which is very nice to have with a silnylon tarp - in a wind the tensioner keeps the tarp from ripping and overnight silnylon sags a bit, so the tensioner takes up the slack if you stretch them when you pitch. Opie also sells a continuous ridgeline if you pitch between trees - also knotless, can be used with toggles you bring or just sticks you pick up off the ground. I was dubious about the prussiks holding, but they stand up very well under tension, and I have used the line in 10+ hours of ongoing rain. If you have questions email Opie and he is very helpful.

My usual tarp on the ground setup involves a trekking pole, groundhog stakes, no guy lines, and a whole lot of rocks over the tarp corner guy out loops. Having the wind yank the corners of the tarp off the stakes because you did not put fifteen pounds of rocks on the corners when the wind is gusting from all directions was the only real problem I had.

I'm sorry you don't like what information you're getting... but there are reasons we all use what we use, and a lot of it has to do with the environments we choose to hike in. Clearly you haven't been holed up for 72 hours in driving sideways rain bucketing down on you - let's hope you never are.