In situations where a car door is opened and subsequently hit, fault is generally with the person who opened the door. There are scenarios where both drivers may share liability and each situation is different, so it's difficult to say with any certainty where fault lies.
Since both of the damaged vehicles were a result of the same incident then it's likely that your insurance company will only consider the entire claim one accident. Our State of Insurance report shows that at-fault accidents have an average impact of $899 per year in additional premium in California.
It really will depend on what you mean by "car loan" insurance. If your finance company added comprehensive and collision coverage to your monthly car payment because your insurance policy canceled then you'll likely be covered only for the remaining amount on your loan.
Your auto insurance policy is intended to cover your liability while driving a car. If you are liable for damage that does not involve your vehicle, you would need to file a claim with your renters or homeowners insurance company.