the wood looks like the surface of the moon (a slight exaggeration).
Oak is an open-grained wood and will always have some irregularity to it even if the surface is very flat.
With an open-grained wood if the final goal is a dead-smooth shiny finish the grain should be filled prior to varnish application.
I applied the new stain, and an application of Watco Rejuvenating oil.
Because you don't know what's in Rejuvenating Oil it really shouldn't be used as part of a finishing regime. It's intended to "[restore] beauty, warmth and luster to previously oil-finished surfaces".
Given what it is likely made from (I'm guessing) you should be fine, but there is a chance it could cause problems later.
Better to have used boiled linseed oil at this stage to do what I presume you wanted here, but because you're working on oak it's likely there'd be no benefit gained from oiling and going straight to varnish after the stain dried would have been acceptable — varnish is already quite oily and the first coats 'wets' the surface very similarly to straight oil.
(sanding with 320 between each layer).
You don't need to sand between layers of varnish. The only reason to sand between coats should be to de-nib the surface, which is needed less in the case of wipe-on because it dries a lot faster than full-strength varnish.
It dries faster because it's been diluted and as such you're putting on less with each coat. By sanding each application you're removing some of what is already very little added varnish.
but I am concerned that if may never give me the glass / reflective finish I am looking for. 10 layers of PolyU Gloss?
You really shouldn't be using wipe-on if that is the end goal. Wipe-on is generally intended to provide a lightly finished look or even an in-the-wood finish where there's nothing much on the surface, not a fully developed varnish coat.
One coat of regular varnish may be equivalent to 3-4 coats of wipe-on. And with regular varnish it may require 4-6 coats to build a thick enough coating that you can sand it out and polish it....... you do the math :-)
It would be much better if you switched to regular varnish and brushed on some coats, let them dry and then get good and hard (wait at least a week but leaving it for a month wouldn't hurt) and then began the polishing process.
Related info from previous Q&As:
What is the difference between "curing" and "drying"?
Issue sanding between coats of polyurethane
How do I achieve a "piano black" high gloss finish on wood?
Note: this is a tough finish to pull off so prepare yourself for some work! But to be honest if this is your first time doing this working towards it directly on the project piece is very risky. It's much better to make some of the mistakes that first-timers usually make (#1 being sanding through somewhere) on something less important, or better still on a test board or two that don't matter at all, than to commit to doing this on a desk you care about.