Q2A (Question2Answer php script) plugin modification

General information for the website: Questions and answers
Kind of development: Customization of existing website
Description of requirements/features: I am building a Q2A (Question2Answer) based website - it is installed and ready for use with mock-up questions and answers.
The Q2A script allows external plugins. One such plugin is Star-rating, but it no longer works with Q2A version 1.7.3. (author admitted there is a coding mistake but never fixed it)

I need the following:
1) fix Star-rating plugin (install 5-star rating for answers instead of votes)
2) only question author and those who added the question to favorites are allowed to rate; can't rate own answer
3) allowed to rate only once (it's possible the plugin supports that but since it's not working I couldn't test)
4) (given that Q2A script supports a points system) for every five maximum ratings - 1 point given to answerer, all other points remain disabled
Extra notes: