Well....you could use Boot Camp and install win doze 7 on your Mac and still be able to run 8 LE. --> Installing win7 with bootcamp

Or upgrade your ProTools with a perpetual license, which will be expensive. You could also subscribe to the latest version of ProTools (12.5) either monthly or annually. Just remember at the end of the subscription, you will no longer be able to access that version of ProTools.

Also, if you are running El Capitan 10.11.4, there have been reports of driver issues with the 11R. ElCap 10.11.3 is supported for the last 11R driver release. So you may need to test that and perhaps downgrade.

No good news for you there. Sorry.