What would help is if when I build ships, I could designate what base I want them built at but I can't. The system arbitrarily picks bases throughout the system. I need a concentrated troop count and I'm not getting it simply by creating new fleets as they're being put all over the place.
Select the base you want the ships built at, then use its build options to order your ships. Alternatively, open the Construction Yards menu in the upper center area of the screen near where the Designs menu, Ships and Bases menu, and Construction Orders menus are, select a shipyard, and use the build options there to order your ships.
Designs are maxed out from what I can tell, so I'm already going as fast as I can go.
Okay, then start stripping off unnecessary components and replacing them with fuel cells; if you've secured the target area, you don't need much at all in the way of armor, shields, or countermeasures, nor do you need weapons or targeting components. Or switch over to Fusion/HyperFusion/NovaCore Reactors from whatever less efficient reactors you may be using and install Calista-Dal Warp Drives instead of Equinox Jumpdrives; they'll take longer to get there, but as long as the static requirement is below ~50 your ships should be able to go further afield with Calista-Dal Warp Drives than with Equinox Jumpdrives, though be aware that the range gained might not be that great.
Okay, here's where I'm at. I tried the refuel route but there aren't any close bases between the fleet and the target. When I ran out of fuel and chose the refuel at nearest base option, it took me farther away from the target as that was the closest base. So I'm going to have to try something else.
Grab a couple of resupply ships (or build some, if you don't have any), load them up with fuel by deploying them at an appropriate location, then redeploy them at convenient points on the way to the target, perhaps even at the target. You now have refueling points close to the target. Problem temporarily alleviated.