Just do it, I brew with a 3 burner single tier on my porch about the same size as yours. All windows are also screens. I am using natural gas though. I have been doing it for years. No issue with anything. If you are doing a single burner get a full sheet tray, used in restaurants for boil over. "safety" guidelines are there because a lawyer created them for liability. I would brew on your porch as long as it is always supervised. I know others will tell me Im wrong and you are but your point about having your oven on is ok but a single low pressure burner is the biggest no-no is well understood by me and others. I have had natural gas stove inside with no exhaust fan. And a LP oven with the same situation. I would suggest getting a long LP hose and put it as far Away as you can. My new setup is back to low pressure LP and I'm indoors but the tank is outside.