ScottStearns

Found your exif. 1/800 f4.5? iso64 @200mm I think you had to do some serious shadow recovery in post for this at that iso. Or, does LTT do any weird compression crap like FB does? In camera I would suggest risking higher iso to balance a higher shutter speed and/or aperture. I don't think the potential lower noise is worth that loss of detail in shadows. Plus bumping the other two up will clean up your edges. I like the comp, the mid day light, and the blue!
 
 
Focus Stacking Practice.
About 40 photos to make this. Not quite enough to get all the way back. I started too far forward. 
I'd love suggestions on post processing stacking. In particular, I'd like to mask in/out manually on rendering errors (like the front left foreground of the base of the subject).
I'm not sure this has exif so: I used Canon's old 100mm 2.8 macro (not L), at 2.8, 1/250, iso50, one step at a time with Magic Lantern. Render B in Helicon Lite with no edits beside basic in LR. I used one large softbox with 1/32? flash 4" directly above subject on white foamcore.
 

Consider grabbing a hot shoe/tripod mount adapter: B&H has 'em for about $12.
https://www.bhphotovideo.com/c/product/764588-REG/Nisha_HTS_T_Hot_Shoe_Tripod_Mount.html?ap=y&smp=y&lsft=BI%3A514&gclid=EAIaIQobChMI1c3NrKqo5AIVjYbACh0pwwZtEAQYESABEgKKgPD_BwE
 
Depending on your use case, this lets you put the flash on a stick (like one extended leg of your tripod) and hold it out into line of sight for the optical trigger. Then you, the camera, and the flash are all functional and portable. 
 
Or, pick up this to tripod up the flash, cheap modifiers like umbrellas, whatever, on the tripod. Then you can place your light and hold your camera.
https://www.bhphotovideo.com/c/product/546375-REG/Manfrotto_026_026_Swivel_Umbrella_Adapter.html?ap=y&smp=y&lsft=BI%3A514&gclid=EAIaIQobChMI1c3NrKqo5AIVjYbACh0pwwZtEAQYEiABEgKvTfD_BwE
 
Have fun with ND filters and rear curtain shutter flash syncing stuff :-)

This is tricky, you have two very different use cases. You could run the audio side with a ten year old $100 Thinkpad t520 and it would run Cubase, Audition, or whatever just fine.
Add in the video and now you need some real horsepower, but you already know the $$ issue there: the gpu. So, this is my attempt:
 
Intel Core i5-9400 2.9 GHz 6-Core Processor $185
Asus PRIME Z390-P ATX LGA1151 Motherboard $140 - several on Amazon for $100
Samsung 970 Evo Plus 500 GB M.2-2280 NVME Solid State Drive $118 -whatever else you get, get this! It's enough for your OS, apps, and working files, and you will love it.
SeaSonic EVO Edition 620 W 80+ Bronze Certified Fully Modular ATX Power Supply $80
Throw in the GT710 and an air cooler for your cpu and you should be right around your budget. 
 
For $340 you could get the i7 8700K, which i think might be fantastic for your workflow. I know you're not overclocking, but you'd be arguably only one step away from the top cpu for z390. Premiere loves clock and cores, and I think it's using hyperthreading better now. Drop the cheap gpu and use the integrated hd630 that both of these cpu's have (it pushes to my 2K monitor fine but I'm not playing games), look for deals, and you might still stay in your budget. Close anyway. It should be just fine until you grab your 1660.
 
Don't worry about future proofing. It's not a thing.