You're asking sensible questions. Amongst those that you haven't asked:
How to heat the boat? In order of expense, probably LPG > diesel > kerosene (needs a second tank) > solid fuel (coal / wood). Electric is probably a bit cheaper than diesel but not usable if you go cruising.
Hot water? An electric immersion is probably the most economic and convenient if you're in a marina, usually fairly easy to arrange if it's not already in the calorifier. A 1 kW immersion left on for a few hours may be better than a larger, domestic sized one used for a short period.
Ask away...