When I bought my car I had almost the same issue. No forward movement in any gear, and reverse worked with no problems. Here's what I found on my rebuild.
4th clutch shaft splines stripped,
3rd gear clutch pack friction material in pieces.
Input clutches worn down on the edges
Outer input clutch apply piston seal stretched
1-2 coast band worn down to the metal in some spots
3-4 apply band broken
All clutches had black rings burned into them.
So I think its time to source another trans. Keep the one you got and pull it apart so you know exactly what broke.
