You'll need to look up the actual consumption of the various things you want to connect, but I suspect you're probably in the right ballpark (depending on just what sort of furnace you've got), but the cooktop may be dicey (but a microwave will probably suffice).

Whatever you do, hook this up properly, no suicide cords, no backfeeding of the grid, etc...

Assuming you intended to say 6000 "watts", I can tell you that 6000 watts beats nothing by a whole lot, and with a little common sense you can probably run the items you listed.

If you really meant 6000kw,(6 MW) you will be able to run a good sized town. It will, however, be a pain in the rear end to move.