Breaking this agreement by the Kurds will not do anything good for them and will endanger their enclave in Aleppo.
As for Israel -- I'd not call this "violently opposing Israel". :P Let me call this "violently verbally opposing Israel" instead. The border was almost totally quiet for 40 years. Furthermore, about 5 years ago there was a prepared peace treaty (Israel returns part of the Golans but keeps the strategically important heights); this agreement was killed by Mr. Obama.
Actually, looking back, that description is more accurate.
Assad did not respond with force to a small number of Israeli surprise preemptive military strikes on Syrian territory, facilities and citizens.
You are correct, Assad has been responding to Israel verbally.
Doesn't this mirror Assad and his father's historical policy for some other minority groups in Syria (like Christians)?