I had the same complaint with mine (although j20a) until i changed the clutch two weeks ago.
I found the fulcrum pin was punching through the fork.

The clutch had signs of wearing thin for a while, like you describe trouble selecting reverse, and slow to shift in 1st and 2nd as the plate was not fully disengaging.
The one I replaced was an OEM Aisin, down to the rivets, probably the original clutch ,180,000km. I replaced it with an OEM style Exedy clutch, replaced the fork ($45 from Suzuki) and spigot bearing.
Now I have a nice light clutch pedal and my left leg thanks me for it.