1. This is grammatical, but it is not very idiomatic English. I'm not sure when or why you would say this.
2. Again, grammatically correct, but not idiomatic. Perhaps: An effective way to solve/reduce the tension between them is to separate them.
3. OK. "I wrote a new script for our play" would be more natural.
4. were, not was. Otherwise, fine.
5. "the leather was too taut."
6. OK, but replace the comma with a semicolon (;).
7. cup, not cap of tea. I agree that casually is odd. Perhaps, "She accidentally dropped..." Your use of "so" is fine. If you write "therefore," you need to precede it with a semicolon, not a comma.
8. This is fine.
9. He inflicts pain on her, OR he causes her pain.
10. I agree with David's corrections--but I'm not sure I understand the meaning. I think you mean "she acts in his play." "Spectacle" can mean a number of different things in English.