You are going to want to put the seat release handle back on to do this.
As I recall, your seat tracks are stuck. Spray a penetrant like PB Blaster into both seat tracks from both the inside and the outside of the seat. Spray it into the track from the front and the back. Work the seat forward and back to loosen it up. The penetrant will loosen up the dried grease and dirt in the tracks.
Slide the seat back to reveal 2 of the 4 seat latch mounting screws. They are flathead screws going down into the floor. Remove those 2. Then slide the seat the other way to reveal the other 2 and remove them.
Now the latch is no longer attached to the floor. You can work it out, using the handle to turn the shaft 1/4 turn to release the teeth from the bracket.
You will see the seat base is held down by 8(?) square nuts, 4(?) on each side. Remove all of them and the seat will lift off of the tracks.
Now you can really get in there to clean the tracks and get everything sliding smoothly.
When you put it all back together, don't forget to install the large spring between the lower latch bracket (screwed to the floor) and the back of the seat frame bottom. You will find small holes that the spring ends slip into. This spring is often missing. It serves as a assisting force to help move the seat forward when you want to do that. Here:
https://www.snydersantiqueauto.com/product.htm?pid=978902&cat=41740
There is also a small spring attached to the adjuster to pull it back and hold it in the locked position. If you don't have it, you should add it. You can see it in the picture for this product (the full latch):
https://www.snydersantiqueauto.com/product.htm?pid=978901&cat=41740
After cleaning the tracks, lubricate them.
Hope this helps.