I have not long had my first boat (Honwave T40 and Tohatsu 20 4 stroke) and I think you will soon get fed up with a 3.5 to 4 meter air floor with that size engine. The tohatsu 20 is really too heavy for one person to carry and if laid flat has to be kept with the tiller side up to avoid oil damage, getting it in and out of a car like that would be hard work. The Honwaves aren't much lighter at that size either.
The pump that came with my boat is next to useless, it is impossible to get a good seal with the valve and when you switch to the high pressure output it takes ages to get any air into it.
I bought a Snipe inflatable boat trailer for mine (Snipe Trailers and Cradles
) and leave it inflated with the engine on most of the time. If you don't want to tow then I would consider a smaller engine.