All of those young players you mentioned signed new long term extensions this season and will be contracted for 3-6 years. We don't need to find extra money for them any time soon.
We aren't throwing the farm at Jackson, even Melbourne were gearing up a $7-800K per year contract for him before he confirmed he wanted to head home. As you mention, Fyfe's contract will be renegotiated soon and Lobb won't be on $700K after next season. There's plenty of room to move with our salary.
You also mention the new TV rights deal which will almost certainly see the salary cap increase by a fair bit. We are really well placed in terms of salary cap and having signed all our kids.