I would do two things.

First, I would implement a counterweight to ease the load.

Second, I would get one of three:

1) A servo motor with a build in brake (brakemotor).
2) A servo motor large enough to hold the table in one place against
weight, without overheating.
3) A geared servo motor.

If you recall, I also have a motorized knee on my mill. I have a
geared servo motor that does not slip when powered off, due to gear
reduction. When I bought it, it had no encoder, but it had a little
extra shaft, so putting an encoder on it was easy.

I had to enhance EMC2 to turn it off when not instructed to move for
more than 10 seconds. I wrote that component in C. Without it, the motor
would overheat, trying to push the knee "one last hair".

It works great, as of right now.

i