Is it reasonable of me to ask for my towing fee to be reimbursed by the association since they didn't abide by their own rules?
Sounds like it, but have you checked thoroughly to make sure they didn't abide by their own rules? By that I mean have you read all the governing documents to make sure that the wording you quoted is the only thing in there about parking violations, and there are no exceptions to the policies you describe?
One other thing to check: were there signs in that parking area, warning that cars left there overnight would be towed? If so, that could be considered fair warning that special rules applied to that particular area.
If they refuse, could I file a small claims case for breach of contract?
You should follow whatever procedures your HOA governing documents have for appealing the towing charge. Only after those procedures have been followed and have led to an unfavorable outcome can you hope to sue successfully.
If so, what other expenses would be reimbursable, i.e. lost wages, mileage, etc.?
I don't personally know, but have read that courts won't usually allow such expenses to be included in the judgment. Seems logically inconsistent with what I've read about creditors being allowed to charge debtors their "costs of collection," but I'm no expert in these things.