Can a French speaker learn Haitian Creole more easily than, for example, an English speaker?
Yes, just as an English speaker can learn Jamaican Creole more easily than a Frenchman could. Both are basically a European language simplified and its prounciation and syntax heavily influenced by Bantu languages. But ease is relative: neither would have a very simple task!
Yes. Haitian Creole is a French-based Creole, which means a French speaker would have somewhat of an advantage when learning it over an English speaker. However, bear in mind that Haitian Creole is still VERY different from French, so do not expect it to be easy. You may also have trouble learning aspects of the language that may seem 'wrong' to you, whereas a non-French speaker would not have this problem. So, yes, you'll be definitely be able to learn it, and you will have an advantage, but bear in mind that you will still have to apply yourself just as much as you would for any other language. :)
Not a modern french speaker because the syntax and grammar mixed with french root words is English. It is an whole nother way of speaking.