Mouse- helpful in the immediate. Missed those rules, thanks for the page numbers.
Masurao- I may be overthinking the situation somewhat, but to me, that's the point of a forum. After all, with the situation right in front of me as a GM, I'd likely just rule whatever works best for the game and not worry about it. On a forum, I'll then debate my own ruling.
As for Dresden's getting through the door- absolutely a burglary check. Door is locked, he's trying to get in = burglary check. No external lock or even door handle (as with most firedoors) = burglary by thaumaturgy. Sure, he's bypassing the lock at this point, but he's still solving the impossible problem of getting through a locked door. I'd set the DC as if it were a locked door he could pick with burglary and have him pop it that way. The skill involved in opening the door that way is focusing his mind, and projecting the force through a solid, probably opaque door. At least as much skill required there as for me to do it using a bent metal rod/crook slipped through the doors, turned so the crook catches the latch, and pulling it in... which is one way to burglarize a locked door.
Textbook use of thaumaturgy, and I have no problem with it.
Here I wonder how you would use Thaumaturgy to make Morgan jump like that? There just isn't the time for that. Also, it would be true that he could do it with Evocation and it might cost him stress and some time, but that's just one of the lesser downsides to magic: it doesn't make you physically better easily. If you want to do such a thing on the fly, you could use an enchanted item or potion, or Evocation with a supplemental action to start running (dunno if this is actually possible, though), but it is never as effective as simply have an inherent supernatural power to do such things.
Thaumaturgy doesn't seem to me like it NEEDS more time and symbols to work... just that you can use them to great effect. The text explicitly says that you need the symbols to pull something off without line of sight or at great range or both. I think the time mechanic is exactly for extra juice.
If your Lore is good enough, you don't need to take time for prep.
If your Conviction and Discipline are good enough, you can put enough shifts into the spell in a single action to complete it... in a single action.
If the effect is simulating a skill roll (in this case, athletics), then you get the benefits... in a single action.
See the above with Harry's using magic to get through the door. The door is opaque- which means he's affecting magic without line of sight (manifesting raw force inside the door, where he can't see)... this means it can't possibly be evocation. We don't see him using a potion or an enchanted item to do this, and the books refer to him drawing in his will, and using the staff as a symbollic focus for projecting the force. This sounds, walks, talks, and quacks like thaumaturgy...
Yet only takes a couple seconds (single action), and the benefit is immediate.
Also- not suggesting Morgan change his body- suggesting he make it lighter... not by hollowing his bones out- using gravity magic, well within earth's purveiw. He could just as easily use a powerful gust of wind, if he were good at that.