If you have an ohm meter, you can check to see if there is some sort of path from the center or + terminal in the head to the outer shell of the head. It should read infinite ohms. If you have some sort of a connection then there is something wrong.
If those tabs are the only thing holding the door to the block, I'd suggest carriage bolts long enough to go through to the backside of the blocks and steel backer plates with a nut to hold the door securely.
http://www.cnhuaqi.com.cn/pic/200773156909609.jpg
I EDC a partially serrated which works best for me. Depends on your usage as I may have to cut through several cable ties and the serrated edge is great for that, but I still have a section of plain edge blade when needed.
These would be the least expensive way to go:
http://www.dealextreme.com/details.dx/sku.12160
http://www.dealextreme.com/details.dx/sku.12149
You'd have two separate lights, but bodies are color coded, less than .50 each and anti-roll.
The Streamlight 4AA Propolymer LED Flashlight with seven leds is a nice floody light. I keep one in the car. http://www.streamlight-flashlights.com/4aa-propolymer-led-flashlight.html
There is a better photo and lower price here...
It could also be vinyl protector that you've sprayed on your dash heating up in the sun and leaving a film. That's also why it would be worse on the windshield as most cars have fabric beneath the rear glass.