I'm not familiar with steel offerings. Outside of the custom builders, the vast majority of offerings in steel are entry level (i.e. Fuji Track, Bianchi Pista).

Unless you are in love with those hubs for some other reason, buying into a proprietary hub system isn't practical. Plus gear changes where you gotta remove 6 bolts will be a pain in the butt. At the track, it's not uncommon to change gears 3 or 4 times in a training session or race day. If you stick with racing, over time you'll likely build a full kit of 46t, 47t, 48t, 49t, & 50t chainrings plus 13t, 14t, 15t, 16t, & 17t cogs. You'd start hating that hub very soon either because the gear changes are a pain and/or the cogs are hard to get or expensive. It looks cool, but doesn't solve any problems. The standard cog + lockring system has been working well for decades (maybe even over a century. I'm no historian).

There's a guy that races at our track that rides a similar distance to the train then from the train to the track, races, then back home. Commuting to race not unheard of. He's pretty warmed up when he gets there

There are lots of threads about Leader. I've never considered getting one. My humble opinion is that they are bikes that look like high performance track bikes, but I'm not sure how they deliver with quality, quality control, or customer service. They are uncommon on the track.

I'd go with a carbon track fork (30 degrees). Different forks by different manufacturers perform differently.

Man, you seem to have particular tastes. Nice tastes don't really jive with a $600 budget. A-la-carte get's really expensive really quickly.

My advice: Buy a Felt TK3 or Fuji Track Comp complete and replace things as they break or as needed for fit (i.e longer stem, different saddle…). Seriously. If you start down the a-la-carte build-a-bike it will cost waaaay more than $600 and if money is tight, will take many months to complete. Then you will miss most of the season and spend lots of money. Racing starts in a few weeks.