FWIW, I maintain a handful of SRI/Buck 910s, which do have electronic pressure controls(not flow controls) but otherwise are pretty much as bare bones and basic as you can get in a GC. These are used for teaching labs, and in fact they will probably get ~200 injections each over the next two weeks.
The general design seems similar to what you're trying to achieve. We do on column injections with them-the needle just goes through the septum and into the glass wool at the start of the column.
Our standard column is a 6ftx1/8" Supelco CW-20M. I'm not entirely sure WHAT the packing is in it, but I have a couple of them cut open to use as teaching models. The stationary phase is very white, but otherwise looks and feels a lot like fine sand. It's a fair bit more course than the diatomaceous earth(Celite 545) I also buy by the bucket...
You have my admiration by doing this yourself. I had a professor in undergrad who always talked about making his own GC columns, and in fact his dissertation involved preparative GC on a 1/4" packed column that he'd packed himself.