Ok hope I can explain this.
If you look at your picture I edited. Might be off but you can adjust as need be.
I marked in red where I thought "bow" started and ended, if I am off you will need to adjust.
You want to support under the hood at where the bow ends at both ends. If my picture was right you would support the hood under the red mark in the back corner and under the red mark toward the front. You can use some hardwood in the correct thickness, or some hard rubber, I have screwed hood bumpers into fender mount holes before to support hoods for this.
But anyways support the hood at both ends of the bow, where the hood is good. Now in the back not a lot of room to support hood because it looks like the bow goes pretty close to the corner. But in the front you can support the hood in front of the bow for more than a few inches. After you have good solid support underneath, latch the hood down good so it doesn't move. Latch it clamp it whatever, you don't want the hood moving
Now there will be no support under the bowed part. The blue line I drew is what I am guessing is the length of the bow, again you adjust this to your actual bow length. Cut a 2x4 a little shorter than the length of the bow. Like if the bow was 12" long I would cut the 2x4 like 9-10" long. Turn the 2x4 on it's side (the thin part of 2x4 on hood) and place it length wise over the bow, on the outer edge of the hood, I would have it a little over the edge so the force will be on the part of the hood where the top panel wraps around the inner shell. So the wood just misses the fender. Keep the 2x4 on its side, over the bow (unsupported part of hood) and with the 2x4 on its side over the edge of the bow hit it with hammer. Start with smaller hits and move the wood back and forth over the bow as needed. Sneak up on it if you know what I mean. And don't try to take it all out at once. You may have to hit it hard but try lighter hits first.
For the bow to come out there cannot be support under the bow to keep it flat with the rest of the hood. It will just hit that support and bounce back. You need to have the bowed part go past that point so when it comes back it is lower and closer to straight.
If you get the hood too low you can work it back some or skim it with some filler. If you can't get the bow completely out you can add some shims under the fender mounting flange to have the fender mimic the bow some and it won't be as noticeable.
But bet you can get most of it out.
Hope this makes sense to you, if not clear let me know and I will try to explain it better.
Lou