Dressage saddle for dressage. Jumping saddle for XC and SJ, whatever makes you feel safe, secure and lets you have a good position. I know people who do XC in stock saddles and western saddles because that's what works for them, they have horrible position over fences but and even worse one kn jump saddles hahaha. As long as your position is secure it's your choice
your hunter saddle will definitely be fine for show jumping, and dressage if you are going to stick to lower levels although t may make it a bit more difficult However, if your hunter saddle has a pretty flat seat you may feel safer and more secure in a deeper seat out xc (this would also help with dressage)
You can use your jump saddle for show jumping and cross country but I would definitely get a dressage saddle for dressage.