Hi Thien,
1. Commune and communicate look similar but are not related in meaning. A 'commune' (noun, related to community) is a large group of people sharing a common living place. 'Communicate' (verb, noun form is communication) means to share information or ideas etc...
2. I think you mean 'would' instead of 'should' for it to make sense. With 'would' both sentences make sense, though they mean opposite things.
Your understanding of "If I had helped, I would not have been able to find my way" is correct and " without helping, I would not have been able to find my way" means the opposite.
I hope that helps!