(Forgot if I said this in my reply and can't see as it is being reviewed by an admin before being posted)
What will knowing the account information prove? If the account activity is not mine, then am I safe? What can I do?
The account information may prove nothing. If you are the sole owner and user of a computer and there has been illegal activity on this computer, however, I would not say that you are "safe."
You will generally (but not always) receive notice from your ISP that a subpoena has been issued for your account information. You have only a few days from the date of this ISP notification before the ISP is required to release your account information. If the ISP does not release the information upon receipt of the subpoena, they will be in contempt of a court order.
A response to a notification that your ISP has received a subpoena can be to file a motion to quash the subpoena, on a variety of grounds. For this, you will want an attorney's assistance. Again, you only have a few days to respond to a subpoena that has been served on your ISP, so if you want to keep your account information private, get an attorney to help you with a motion to quash.
Your IP address is used to identify your computer on the internet so whenever you visit a website, there is (generally) a record of your computer's visit. An IP address, therefore, is recorded and can be tracked backwards to a specific computer and the specific date and time the computer was used to gain access to the internet and a specific website or web page.
The IP address, in other words, is only a starting point. The IP address and account information cannot necessarily prove who used the computer, especially if there are several people who use the computer or the network is unsecured, but it can be enough to get a warrant for computer search and seizure.
Evidence of illegal activities on the computer can often be enough to file charges (e.g., pornography) or file suit (e.g., copyright infringement, defamation) against the computer owner/account holder. Even when material has been deleted from a computer, computer forensics can find evidence of illegal activity that has been wiped or deleted.
Again, you will need to find assistance in Ontario. If you are afraid your computer will be connected to illegal activity, it would be smart for you to discuss this with an attorney in your area - and you definitely should contact an attorney if you are contacted by the authorities.
Speak with an attorney in your area before reporting to the police what you suspect might be computer hacking. Reporting to the police that you may be a victim of hacking may or may not be smart.