A magic carpet uses an even friendlier fuel with even less pollution. There's no need to sell it until it works. Everybody already knows perpetual motion would be amazing.

So you have almost no vacuum because it's mostly filled with HHO? Then the HHO's not being generated in much vacuum and you lose the almost all the advantage! If you have a little bit of vacuum, it uses a little bit less energy to generate the HHO, and takes a little bit of energy from the flywheel. Until you can show that the little gain is more than the little loss then you might as well be talking about a magic carpet.

There's no point using waste heat as a furnace unless you have something nearby that needs a furnace. That's no different from any conventional engine which could be used the same way, but usually there's nothing nearby that needs heating. This is a totally unrelated idea to what you're talking about - muddying the waters.