I like the idea of leaving the patio door open... I had a similar setup
(smaller balcony 'room') when I lived in Chicago. I put one of those
two fan units into the window between the dining room and the balcony.
I have no idea what brand, but they are cheap and have two independent
fans in one window sized unit. Got it at Lowes, probably. You can run
them in opposite directions, which is what I did.

If I had to choose from one of the other options, I'd go with the oil
filled heater. I'm happy with the one I'm using in my compot room.
Very gentle heat, and mine has a thermostat built in.



--
Rob's Rules: http://littlefrogfarm.com
1) There is always room for one more orchid
2) There is always room for two more orchids
2a) See rule 1
3) When one has insufficient credit to obtain more
orchids, obtain more credit