1) I'd choose a state for residency that doesn't have state income taxes.
Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington and Wyoming, all have no income taxes. (NOTE: New Hampshire, however, taxes interest and dividends)
2) sales tax on boat. This is dictated by the state that you register the vessel in, in most cases. Consider registering in a state the doesn't charge taxes, or has very low taxes.
Alaska, Delaware, Montana, New Hampshire, and Oregon
3) annual property tax on what?? Charged by whom??
4) Boats are registered where the boat lives, not where you live. I have owned boats registered is several different states over the years. I've never owned a boat registered in the state of my legal residence.
Your best bet is to document the vessel, which has the USCG (Federal) issuing your title). You may need to register the vessel in more than one state depending on the requirements of each state and how long the boat is kept there. If you never keep your vessel in one state longer than that state requires, then you could never have to register the vessel.