Yeah try reverting back to the setup that you know worked for you and try it again. Once you get a working setup then make a copy of your entire GTA IV folder for a backup. it will take 10-20 minutes but is well worth the time if something goes wrong again. Then you dont have to re-install the entire game and redo all your mods again or try and figure out what the problem mod is. Make a copy every month or so, depending on how much you update your mods that way you always have a recent build. Another tip: when your installing mods, install them one at a time and test them in game. That way if there is a problem you'll know exactly what mod it is.
I was under the impression and I think everyone else was too that you couldn't get the game to work at all. Now with the updated info that it worked and then didn't after the install of mods, it would be almost impossible for anyone to tell you what the issue is even over teamviewer. Plus your diagnostic report is flawless so chances are its just a bunk mod
You need to get a hold of someone willing to teamview you and then set up a time for them to try and help you. You should make sure you try all the suggested things in the support forum and run the diagnostic tool to make sure you have everything. The meeting thing isn't that big of deal, dont worry. Were just discussing it among ourselves :)
I agree 110% cp702 - people are not the same online in real life (not everyone at least). You can't really "know" a person until you meet them and have that contact in person. Thats just my thoughts on it. People act differently online, I use to play online with a buddy who I was friends with for years prior to us doing online gaming and he was different online than if we were together in person
Try going to your Steam, Right Click On GTA IV, Go Down To Properties, Click Local Files, And Go Down And Click Verify Integrity Of Game Cache.. It will fix what need to be fixed in GTA IV once that finish doing what it needs to do try to access GTA IV..