It's about time my parents find out about my felonies and throw me out of the house
The way to "convert" this to future tense would be:
It'll be about time next month when my parents find out about my felonies and throw me out of the house.
We use "it is (or it's) about time" or "it's time" to discuss something which we feel is overdue, and which, we feel, ought to happen now or in the very near future. It is followed by verbs in the past tense. Your sentence should be 'It's about time my parents found out about my felonies and threw me out of the house'.
Past=present or future:unreal uses of ...
From the examiner's comment, I am inferring that there is a passage of text that your answer is based on. The examiner is saying when talking about things mentioned in the provided text, use the same naming convention.
For example, if the passage talked about a character named "William Jones", don't then refer to him as "Bill J." in any of your answers ...
They all have unique meanings which a dictionary will tell you. However, they can be interchangeable in certain contexts.
"Can" indicates that something is a possibility eg. "I can go to the shops for you"
"Could" indicates a possibility that is perhaps dependent on something a condition eg. "I could go to the shops for you if I can borrow your car"