You would get more out of the 90's by doing double front hard, start turn by letting up right, lock in with harness and then finish on double front slowly letting up once on final. You will have to try it up high to figure out how much more altitude the turn will take.
This is what I'm actually doing. I'm going to try and get more aggressive with it. I am finding the FR pressure builds very quickly on the Sabre2. I have landed a few times with really sore arms when I tried hanging on the FRs after initiating a higher turn than usual. Still I feel there's more work to be done to squeeze more performance out of the 90.
I am no expert, and I don't have that much more jumps than you. But I've been told that a slower turn gives a longer recovery. Someone correct me if I'm wrong. And I also agree on what was said earlier about making it more smooth. Smoot input simply makes you swoop longer if done correctly :-)
To the op like a few people have said less snapppy with the fronts especially letting off them. I remember flying the same canopy/ near same loading back around when I had 300 jumps and looking at old videos now it always seems so close to the ground compared to now when turns are much higher on different wings/loading. I think all of us lose some of that perspective as we have progressed to smaller wings and bigger turns and forget what a 90* turn at 350ft on a sabre 2 looks like.
Its a great canopy to get all you can from and I highly encourage you to do like you said and keep getting all you can from it and then move forward after. Get some coaching from a knowledgeable person with experience in person also, they will help you refine techniques and progress to the next level. Internet is a great tool but wont teach you what you need to learn to stay alive. coaching is a small price to have that knowledge that will let you go home to your family later in the day
start with medium to deep brakes (play with this up high), feel the canopy surge forward, then move to double fronts, offset lock in with harness or with bringing outside arm into line with inside arm fly your fronts out (meaning dont just drop them) you will get a longer recovery arc. DO this up high or it will bite you in the ass.