Assuming you are saying the light works. Assuming the mercury switch works. Assume the switch is in the bulb socket area and not on the firewall
.. Therefore place lamp on the inside of the hood, as you did, and tilt it until it goes on. That there would be the angle it wants. So bend, beg, borrow or steal a way to mount it at that angle. Pretty simple.
What is that cylindrical black object wired into the pigtail wire that is seen on the firewall? I do hope that is not the mercury switch.
Yes new mercury switches are available. Not exact.
This is a glass encased one, there are also potted types.
Assuming "high angle" means if the hood opened farther, it would light.