Playing easy and difficult QTE off, but I can't get the Ballista to work. It charges a little bit then a cutscene with re-spawned enemies.

Keep on doing it, eventually it will launch. Use the Ballista, fight the enemies, go back to Ballista and use it, fight the enemies, and keep on repeating till the ballista launches.

First, kill all the guards. Then you "charge up" the ballista.
Second, kill the new guards. Aim the ballista.
Third, kill the last group. Shoot the ballista.

Voila :)

Not sure what 'spam' the mouse button means. I click as fast as I can and it gets up to 80-90% max. I've done this many a time. I'm beginning to think i'm too old(64) and slow to do this.

Hmm Well you do not need that many presses on the mouse... If you have problems for some reason it might be your mouse that dont register the button presses.

"Spam" does mean "click it as fast as you can," so you're doing the right thing. Most of the game isn't like this, so you just need to be able to get past this part. You could try having a cup of coffee. :-) Or get someone faster to do the ballista for you, so that you can play the game.

You're SURE you have "difficult QTE's" turned off?

Sorry, Wizgeorge, as Coylea noted, 'spam' does mean to press as fast as you can. I found it difficult as well (I sometimes have troubles with that type of thing even at 47 years old), but I managed to get it done after three or four tries.

If you're finding it a real issue and just can't seem to get through it, I believe there's a small program you can install that will mouse-click for you. You can map it to a specific key on the keyboard. I can't recall the name right now, but I'll see if I can find a link for you.

It appears I can't click fast enough at this time. Just curious, but there is an icon at the top left of the screen that has 'skip' next to it.. I can't find any reference to it or function.
By the way, I really liked Medical Problems.

The skip is for cutscenes.Can't use that in QTEs.
Try lowering the resolution or the graphic settings completely.Maybe your game is "lagging"so it's not registering all your clicks.Also don't pull your finger off the mouse button,if you are.Losing time that way.

Finally made it with the help of my son.. Got the wheel that opens the gate after 10 tries or so. May finish the game by XMAS.

I know it may appear to be strange, but lowering the graphic setting helps a lot for the QTE that do not 'queue'properly the mouse click. With better frames per second, you will find that the bar will fill very quickly compare to a lower frame per second setting.