Lots of stuff here that I find interesting, as I have a similar space - including a support column in almost the same location.
There's nothing wrong with being a loop runner if that's your objective - it can be very relaxing. Curves, elevation changes, and scenery can add to the interest. Having a few sidings for accessories or industries can allow for an occasional change of pace. Running a point-to-point railroad isn't for everyone.
A lot of planning can be done just with pencil and paper, especially since you'll probably end up using a lot of flex track.
My only specific suggestion is to accept the fact that you'll probably do something that you will end up wanting to change, so don't ballast the track until you've let it run for awhile.
