On the flashing candle here is what it says in the IGT PE+ manual that -tilt- provided in the other thread (were you able to download it?). The machines can have a 2 lamp, 3 lamp or 4 lamp candle. From your photo it looks like your machine has a 2 lamp candle, with red on the bottom.
I'm not sure what all can cause the different door open message or conditions, but besides the main door, there is sometimes a door sense switch on the lower cabinet and on the cash box. Have you found any wires not connected down inside and have you found all the security switches? The manual may list all the various security switches and door sensors. You can look closely at each security switch and make sure it isn't mis-adjusted and telling the machine the door is open. I think many owners bypass the security switch by connecting the 2 wires together to prevent nuisance door open problems.
Also, you may be able to go thru the Diagnostic Test and see something amiss. You can press the white test button inside machine and screen will display various diagnostic and information screens. Basically, if the machine is happy when it powers up and all security checks are ok it will then accept a coin and give a credit for the coins inserted, up to the max coins allowed. Then you press a button on the player panel to bet a credit (or max credits) and the machine will deal you a hand of 5 cards.