Clutch release problem

You have several problems.
1) is insufficient plate departure.
2) Your disc is probably a little warped
3) Your blocker rings are NOT biting hard enough on the brake-cones, and
4) you may have the wrong pedal ratio, or "stiction" in the system.
5) your leg may be having difficulty over a certain range.

As for solutions;
IMO; I have no respect for synthetic synchromesh oil. But to get it all out, the Trans has to come apart, and be thoroughly washed out.
At that time, you can replace the failing blockers, tighten the strut springs, inspect the forks and external linkages, Address the dragging clutch, check the TO-bearing, install a BB pilot, and dial-indicate the BH, looking for parallelism and concentricity.
Finally, you need to get under the dash and verify that you have a V8 pedal ratio, and that nothing is binding, and if you have a Diaphragm PP, that the over-center spring has been removed.
As to freeplay, you can run as little as you like as long as the TO bearing stays off the fingers. and, make sure your clutch-fork, at rest, is as far towards the rad as is possible, and you can still get the rubber boot installed. If this is not the case, something is wrong. Most likely, the fork pedestal is wrong. and if it is, then the adjuster will be wrong too, or it has been modified, or the Z-bar is also wrong/modified. So, there's that, lol.
If your car was originally a six-cylinder manual trans, then more than likely, it still has the six-cylinder clutch pedal, which is gunna have to be either swapped out for a V8 one, or modified to the same ratio..

Going back to synthetic oil;
My opinion comes from my experience in trying to make it work, and taking the trans down FOUR times in two weeks to try and make it happen. The fourth time was just to wash it all out, one part atta time.
My conclusion was, that it was just too doggone slippery for used brass to grab even deglazed brake cones. I tried everything!
After I washed it out, I put my original cocktail of 50/50 dextron2 and 85/115 extreme pressure oils, back in, and then, the thing shifted like lightning, and no more waiting for the N>First shift, nor did I get more than an occasional noise on the N>Reverse shift.! I learned my lesson.
Others have other stories.

IMO, the A833 gears are pretty doggone heavy, and if you have a light oil in the box, those gears continue spinning for a long time. Add to that a slightly dragging disc, and not enough departure, and you can be waiting several seconds to claim reverse without grinding.
ATF will squeeze out of the Synchros the quickest.
140 wt Extreme Pressure lube will be the slowest.
Synthetic is somewhere in the middle, but offers superior cluster-pin protection to ATF.
I have been very happy with a 50/50 mix of
ATF and 85/115EP . the EP oil is for the clusterpin. I have run it down to 25% just to see if the brass could shift quicker, but on the street, could not tell any difference, so back to 50% I went.

Make sure your BH retainer opening is the correct size for the retainer on your trans, and before you take the trans down, make sure the z-bar is;
parallel to the ground and at very near to at 90* to the centerline of the car, that the fork is near the front of the opening in the BH, and, that the Z-bar is fixed in position on the frame end, by the horseshoe-wire locked in the nylon bushings.