defeating fold

I would say if you can't get your hands on the guard, you are now feeling pressure from the outside (T blocking down). If possible fight pressure and squeeze the hole down. When the time is right, cross face and make the play. The LB is the one who should blow this one up, in my opinion.

I am not sure what defense you are running. I would say the time to cross face is right when your gap is no longer threatened. This would be kind of like last minute before the back is in the middle of the hole. You have a good d lineman if he can make that play consistently. hopefully he can get his hands on the OG and slow him down a little.
The blitz would be an okay idea. I would rather just slant my d line or stunt them. Could you put your DE in the C gap, 3 tech in the A gap, and LB now has B?
Just some thoughts.

Your d-end who is in a 5 or a 6 versus a TE, should squeeze the down block of the offensive tackle, this allows you to constrict the running lane and get penetration......:gift;

Coach Scott, sometimes being over TECHNICAL can cause you to get your RESUME together...There is a reason why offenses run the fold scheme versus shaded d-lineman, so I don't know if there is one way to skin this cat....you will have to come up with more than one counter move...if you do the same counter all of the time, the offense will have a more effective counter waiting on you on the next down...you said that you base out of a 4-6 (3-0-3)look...have you ever tried using directions to get to this look as a compliment to your shaded front? For example, you could align your DT's in 4's and pinch them inside on occasion and have them attack the offensive tackle on others...when they are attacking the offensive tackles, your backers can read the windows of the offense(guards)..so if the guard pulls outside(fold)the backer can counter by scrapeing outside to find a more effective run fit....Remember it's not what you do, but how do it...and always keep the offense off balance by tweeking your attacks........