Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

Cam Lobe Lift looks right. But as far as the other measurements --- I have no idea. Mercury doesn't publish any of these numbers. Also I don't know if I would trust that the TDC that you're going off of is correct. The outer ring that's marked with TDC can be off. They can slip a little. The only way I know how to check this is with a dial indicator on the top of the piston #1 or #4, rotating the crankshaft clockwise and stopping about 3-4mm before TDC, mark the balancer and then rotate crank counterclockwise and stop at the exact measurement as before, mark balancer and then split the difference to determine true TDC. I'm not sure this could be done with the cylinder head still bolted on (I've never tried it). This is how it's done with the old 2 stroke outboards, but they have the plug hole pointed straight at the piston. Maybe someone reading this has and could speak up? I'm also not 100% sure this would be necessary to determine if the timing chain jumped a tooth.

You might try calling the consumer support number I posted earlier, maybe they can help with the cam timing questions? Or maybe someone has posted cam specs that might apply to your engine. I'm unable to help with these questions. About 30 years ago I stopped spending my or other peoples money chasing more horsepower. I learned that if you want a faster boat --- buy a faster boat, after good propping and a few minor bolt on things --- it's usually cheaper and better.

I will be very interested to see what happens once this is back together and over revved to see what happens.

TDC was correct confirmed with inspection camera. First set best what I saw on camera and then checked TDC.
Emailed Merc but seems that they wont tell anything more than is in service manual or published in bulletin. They told me what should be fuel pressure but nothing about vacuum or cam timing measurements. They suggested to run leak down test and get Merc dealer to perform G3 checks and proper propping procedure.

Checked that procedure and according to that and previous diacom reading I have to drop prop pitch.

Yes, I didn't think Merc would help you much but I was hoping they might be willing to help due to you being in the EU.
They always ask for a leak down test. If I feel one might needed I will usually do a "dynamic compression test" instead. On these I/O engine I find they are just as informative and way faster and easier.

Suggest you try a Merc Black Max 15X17" p/n 832828A45 it will come with the hub kit for $267.06 US

This is based on what I have seen in the REC files.

I just looked up your Ballistic prop. I'm surprised someone would recommend this prop for your application.
Looks like the Ballistic uses the same hub system. If it's exactly the same you could look for a Quicksilver brand prop. It's the same as the Black Max but called Black Diamond and doesn't come with the hub kit, so a little cheaper.
p/n QA1912X $192.38 US