As you can see my rig is almost the same, 2500k OC to 4.5, W7, SSD for DCS.
After reading all the things you have done im clueless. I can only mention what things caused me the few crashes ive gotten in the past.
Install new graphic card without using DDU first.
Using specific drivers versions, only very rare. Best for me 399.24.
Using very old mission from previous DCS versions.
Using mods not compatible anymore.
Editing files inside main folder that new DCS version dont support anymore.
My advice If you have not did that already is try a fresh nstall both DCS and users DCS folder.
I mean. Cut and paste your DCS main folder and users DCS folder to a separate driver. DeleTe EVERYTHING DCS related after where you had original installed DCS both main game and DCS folder inside users.
Reboot.
Download latest release versión installed and Install DCS from scratch but only the stock game. Not modules, not terrains, just DCS, as it is without extra content.
Reboot after instalation.
Run DCS for the first time and see If you are able to load the game. If you are able, try to fly some time in the Su-25T. Look for issues or not. If not, Install one by one your modules and try to load-fly.
I know is very time consuming but i cant think in anything else.