Cap hold fro Steisma doesn't count against Apron.
I had them at about 67m with JJJ, Moore, and Williams, but without any cap holds. Since sending out Moore and Williams clears 1.5m, they could take back about $8m.
Yes they may get some relief from the structure of KG, Terry, Bass, & Green (as well as the structure of Camby & Lee deals), but they also may have some additional costs not reported (unlikely bonuses, benefits, etc.) They could also S&T for Terry with Dallas instead of using MLE. Use MLE on Lee. He may like a make good contract with a contender.
He played his best with ORL in his rookie year - getting on a defensive oriented team, where he has a PG creating open looks for corner threes and fast break buckets, might raise his profile and market value. Given AB is out for start of season BOS presents a nice opportunity for a one year deal, like Posey signed in 2008.
Update: also in a S&T for Camby if he's only playing two more years, they can give him a retirement contract, that pays him a third year. Won't matter for cap purposes, might be useful for trade purposes, and raises the value of his deal. It's what they did for Sheed.