bit and new saddle help!

Is he leaning on the bit? My draft used to lean, and be heavy in the fore. I do not do dressage, so have no idea what is legal, but I used a Waterford mouthpiece which is more difficult for them to lean on. I also "drop" them when they try to lean, but since you need constant contact in dressage this may not be possible? Pulling back against a horse is always a losing battle, no matter what bit you use.

You can still "drop" them when needed in dressage. It's part of learning self carriage and reaching, not leaning, for the contact. ;)

I use a senior eventing saddle for all 3 phases as judges cannot judge on tack, and it works for all phases for me. Plus is comfortable and lasts a long time. My trainer had hers for 20 years and counting!

Try adding a crub chain

Try adding a crub chain and spurs for led enforcement

^ You cannot use a curb chain with a snaffle in dressage, nor would it do anything with a non-leverage bit.
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OK, I think you have 2 problems here, your horse doesn't like a particular bit, so going to a stronger bit is NOT going to help.
Many horses lean on single jointed snaffles because the single joint hits the roof of their mouth, that hurts more than putting pressure on their tongue/bars, so they lean into the bit so that when it V's out it doesn't hit their roof as much. Try a double jointed snaffle like a French link or Lozenge style bit - KK ultra is one of my faves.
As for your horse not listening - this doesn't require a stronger bit - it requires better training. I have a small draft mare who's kind of a 'brute' she's always known she's stronger than people, but after some work, she's very responsive to the bit - I use a french link when bitted, but typically an indian hackamore. I also have a very large Belgian who I ride in a flat halter - he also goes in any bit you put in his mouth, when I get him one it'll be a french link or some equivalent.

If you want your horse to be more responsive in a gentler bit, it just requires more practice and better timing. When riding change things up a lot, use circles, change pace constantly - never make a full lap around the ring without asking for something of your horse. Make big circles, little circles, figure 8s, serpentines, stop and back up, change paces, stretch out and collect your gaits. The more you ask of your horse the more attention they need to pay. You also need to be SURE to give a significant release of pressure when they do the right thing. I see all too often english riders not giving enough of a release to mean anything, they think contact=death grip. I'm not saying you do that, but at the same time be more conscious of your release of pressure. Do these exercises in the mildest bit you can find and over time you'll be amazed how soft your horse is.