1987 Ford Tempo Rough/sticky shifting

I have a 1987 ford tempo that is in very good shape and runs like a cat purring.(Even after sitting under a pine tree for six months) However I experience very rough and regulated shifting and it is only shifting 3 gears. It shifts between 20 and 25 and between 35 and 40 and thats it. After that the rpms just keep rising. At 50 it runs 3k rpms and t 70 3.5. Is that normal or is the tranny sticking (should there be anyother gear? Also it has a rev meter on it and no matter how slowly I accelerate it will not shift until it reaches the above mentioned speeds. Finally when I am going up hill at low speeds and let go of the accelerator the car will shift up very harshly (It almost feels as if somone bumped into the back of you) Perhaps my tranny is on its last leg? If it is just gummed up is there anything that I could perhaps add to the tranny fluid to clean it out or maby get the tranny flushed? Any advise would be appriciated. PS: I'm a college student so if there is anything that is inexpencive that may not fix the problem but will help let me know that also
Please, Thank You, and God Bless

Brian G.