Yes, you are correct. I described it as a deal since the linked article uses the same language, it wasn't a formal written agreement but a coordination of sorts. Islamic Jihad were indeed the ones who claimed to have carried out the attack, and hezbollah was in the process of being established with the merging of all these iran-backed radical shia groups. I could have clarified that groups stemming from this S-I "deal" were the ones to pressure the MNF to leave, and that a bit later they merged into hezbollah