I doubt Syrian missile technology has the required accuracy to hit the Dimona reactor with any confidence. They may launch missiles "at Dimona," as Saddam tried, but it is unlikely that any will hit the reactor. Meanwhile, the Israeli response will be very severe. The Syrians must be very scared of another IAF strike to make such foolish threats.
Iran deal opposition grows among U.S. Republicans, Reuters poll shows (Reuters)
from the article: Syrian MP hints Damascus could strike Dimona reactor if attacked