You can’t tech every throw without getting hit by things. If you stand tech you’re risking getting hit by a low or having a throw whiff punished. If you crouch tech you’re risking a juicy counter-hit combo.
If your opponent gets you to block a jump-in or a blockstring then his reward is the mixup. Accept that there’s a chance you’re going to get hit and take a guess on whether to stand tech or crouch tech depending on your opponent’s blockstring habits.
The timing for throw techs depends on what kind of tick the opponent is doing. If Ryu does cr.mp throw then the timing is obviously different than if he did cr.lp throw.
If you can’t reliably tech throws against a person without getting counter-hit that means your opponent knows how to use throws. So do your best to stay out of that situation in the first place - don’t get knocked down, don’t block a level 2 focus attack, and don’t let him jump in.