I'm happy that the new bit is working out for you.
If I may offer some advice/critique (if not stop reading now
) but I'd really like to see you start working with him on getting him round and soft. He's rather inverted through the neck and hollow in the back, which is part of why his form over fences is somewhat sloppy and his jump lacks power and impulsion. He also seems stiff in that left hip and stifle and perhaps is out of whack chiropractically. He doesn't use his hind end properly when moving and when taking off the weakness in that left hip becomes more apparent as he uses his neck and forehand to sort of chuck himself over the fences.
In addition, it seems that you are quite grippy with your knee and lack a proper lower leg foundation, so as the fences got larger, your position got looser, which eventually led to the refusal at the end. By raising your stirrups a hole and dropping your weight into your heel, and slightly turning out your toes, you can get away from the knee grip position you are doing over fences right now. This will help keep you from jumping ahead and getting dumped off. In addition, rather than jumping the height when your horse is not properly moving or muscled and your lower leg (and as a result your upper body) is not secure, I'd prefer to see work on cavaletti, grids, and lots and lots of grids with no stirrups and reins. I'd also be focusing on entire lessons in two point with a focus on elongating the thigh and calf muscles as you drop your weight into your heel. This will help keep you more secure in your tack, and eventually lead you to be able to take a proper contact with your horse allowing him to propel from behind rather than pulling on the fore the way he moves now.
While working on your position, your horse could also benefit from some longing with long side reins (not too much and I'd have that left hip checked first as longing will simply exacerbate the chiro issue if there is one), and encourage him to stretch down rather than invert and hollow. Initially he will be better off trying this without a rider as it's asking him to use his body in a completley different way than before. As he starts to stretch down and accept the bit, he will be able to build muscles and move off the hind end more. Cheers to the new bit! None of this would have worked in the old bit as nearly no horse will take a contact or reach for/accept that bit!
And finally, please consider checking your saddle fit. Your horse looks pretty narrow and I have a feeling that the saddle may actually be hitting his withers slightly especially over the larger fences in landing, which will only further exacerbate the head in the air/hollow back way of going that he does now.
Hope this helps and glad that you're on your way to a better ride with the new softer bit!