Hard to feel sorry for Russia or Syria after reading the OP. Pretty shitty thing of trying to smuggle in either military equipment, or arms via a commercial airliner.
Russia has zero reasons to attack Turkey, the WW3 theory is flawed. Here's my quick analysis of current world politics: Turkey > Syria (possible) Israel > Iran (likely) China > Japan (not really) Germany > Europe (we are doomed)
Anyone expecting anything major needs to think again.
At the very most, I can see Turkey going into Syria and setting up a buffer zone around the border, to prevent the violence spilling over onto the Turkish side of the border.
It's last military base of any kind in the middle east, is in Syria. They are desperate to hold on to what influence they have left. It;s why they've been so involved in what's happening.
Who's going to use nukes though? If were talking about between US, China and Russia. None of them will risk it. You can bet your ass nukes will be fired back.
Besides, we have plenty of conventional bombs that are almost equivalent to the strength of older nukes, so there's not much point in using them except for a serious last resort and very very very careful planning.