I have a marlin 1894 in 44 mag with an 18" barrel, ported, and without micro grooves.

Was gonna start off with
200 grain Speer GDHP
With 8.9 grains of 231

This load was from page 950 of Speer manual 14.

Any guess if this is a good place to start?

I would suggest a less costly plated bullet like power bond or Extreme ( might be xtreme) or even
missouribullet.com coated bullets. All are good. Maybe with some trailboss you can come up with a good, extremely low recoiling subsonic load.
Dennis