Your Mac is either 8 or 10 years old and it’s had a good run. At some point, you may need to put it out to pasture. There is a point of diminishing returns. I remember when my 1997 Honda Civic DX hit 254,000 miles and then the head gasket, manifold and O2 sensor all need to be replaced at the same time and the car was NOT worth $1600 worth of work. So, I finally bit the bullet and bought a 2011 RAV4. 15 years was a pretty good run.
You would be well served by a 2019 Mac Pro 8-core or 12-core, 96GB of DRAM, a W5700X (when it ships!!! Hello, Apple, WTF!?!) and an Afterburner Card.
The wild card is your credit line and whether or not you can deal with Catalina...check your app compatibility before diving in head first!!! Just my 2¢.