I have enclosed some pictures of what the screen looks like.
Odd, that picture on your computer monitor looks like the BAD picture you described, but if the TV's menu is dark, then its associated with the BM board and nothing else. Order this part if the menu is dark on the TV.
The test pattern on your computer is set too high on the brightness. You can see the pluge test pattern under the RED bar - it should just disappear into a solid black pattern when it's set right
Your TV pattern looks correct, but the menu is NOT controlled by brightness/contrast controls. They are at a preset level by Sony, and that comes directly off the main board, and into the TCON. A Tcon affects menu and picture, a Main (BM) board can give you a good picture, but bad menu since the menu merges onto the picture just before it hits the TCON.
Once again, the problem you show seems to be on the computer monitor. Did we get mixed up on what needs serviced?
Weird dark edges on your monitor seems to show what we call "black crush" and that 1st picture of your monitor seems to show that same issue in the "red faces"
Yet your test pattern on your computer shows the black level has been turned up too high -- did you make an adjustment to the monitor when you created that picture?
If so, and your TV is where you think your problem is...it may be your TV is fine, but not your monitor.
I have not seen a picture of the TV's menu on top of the TV picture. Yet you stated the TV's menu is dark. Please note I can't open XLS files, please avoid information using that format.