With the foot catching thing, as has already been said, I wouldn't use it with the extendi, or rather, not with the lead extended iyswim. I used it to get to and from the area where I let him run looser, and then swapped to an ordinary collar for that.
She sounds just like Kenny in the way she is with other dogs. We think he was taken away from his litter way too early, so didn't learn how to 'be' around other dogs, and then was never socialised when growing up. He wasn't aggressive, but when other dogs see a staffie galloping towards them full tilt mouth wide open in a grin, toungue a flutter, or straining at the end of a lead looking like that, they tend to feel panicky and react, and so it spirals.
I realised that I was so terrified that he was going to be a aggressive (Staffie prejudice) as soon as I saw other dogs I was panicking and waving them away and calling him in a panicky voice and that made him think that I was frightened ergo other dogs must be something to be scared of and so he needed to defend me.
This one time when we were playing and a loose dog came out of nowhere and approached us, I pulled him close to me on a short lead and kept constantly reassuring him 'good boy' good boy and he allowed the dog to approach and sniff him so i kept up the constant praise as well as saying hello to the other dog. when the dog came round to face him he jumped at it just a bit, so I pulled him back and calmly but firmly said no, and the dog went back to the rear end which Kenny coped with, again each time he started to go for the other dog (whenever he got in Kenny's face) I just pulled him back and said a firm no. This was a real miracle and a turning point for us and was all down to how I reacted with Kenny and the other dog, and this had a radical effect on his behaviour. I kept this up any time we encountered loose dogs, looking forward to it as a way to help modify Kenny's behavious instead of being terrified of it.
I have been doing this for about 4-5 months now, and if we are alone in the fields, I will let him off and we play ball which he loves. If we see a dog now, I calmly call him to me and put his lead on, but continue to play ball, and he mostly ignores other dogs. There have even been a couple of occasions when he has spotted other dogs before me, but hasn't attempted to run to them, just brought me the ball! Result. I still wouldn't let him off in a park full of other dogs, but I think that there may come a time when I can, I feel that positive about it, and yet have come from a place feeling exactly as you do.
Sorry it's so long, and I've parcelled up the gentle leader, will post it on MOnday. Hth. 