I am not sure this has been touched upon, however I have to think that after failing to kill Vito Corleone twice, once outside of the office and once at the hospital, with the deaths of Luca Brasi and Bruno Tattaglia, and with the survival of Vito and all his political contacts, Barzini may have been getting a little nervous about this Sllozzo fella himself. As of the day after the hospital incident, the Sollozzo-Tattaglia-Barzini axis had suffered some pretty significant set-backs, and I have to believe that Sollozzo was under enormous pressure to get this thing back on track, or to hit the road, or perhaps wind up sleeping with the fishes himself. When he set up that meeting with Michael, supposedly to lure him into a false sense of security, that had to be Solozzo's absolute last chance to get his operation off the ground. Had Michael gone there and not shot him and McCluskey, but instead told him he wanted his father left alone, and that the Corleones would not be in the drug business with him, Solozzo may have had no place to turn and his allies may not have wanted to push things, at least with him any longer. So for Sollozzo this meting with Michael was literally life or death one way or another, and if you look at how tired and wary Sollozzo appears in those restaurant scenes, perhaps that is why.

Sol was certainly in a very tight spot at that point, but I don't think it was life or death for him--yet. As Michael correctly analyzed, he was trying to buy time to set up another attempt on Vito's life. Even if Michael had said, "I want my father left alone--and no deal on drugs," Sol would still have had at least another chance to nail Vito. I think he'd be given that chance by Tattaglia and Barzini because, at that point, they had nothing to lose. But if he failed again...

Wasnt Solozzo a top narcotics man?
Wouldnt his expertise and connections be vital in building the drug empire for the mob head(s)?

I think he would be given a pass for his Vito blunder and the "hunted one" speech was just for Michael. Solozzo didnt actually believe it.

From the look on Michaels face. Michael didnt believe that Solozzo believed it either.

Sonny had a hundred button men on the street 24-7 looking for Sollozzo so Sollozzo had every reason to be somewhat cautious.

But these were more or less normal conditions for someone like Sollozzo so I don't know that he would have been afraid of the Corleones or of his patrons.

In the novel Hagen thinks that outside of Luca Brasi, Sollozzo is the most dangerous man he's ever met. Also when the family leadership is congratulating themselves on getting rid of Paulie, Sonny cautions them not to call Sollozzo lucky. They all agree that just as they would not be afraid or worried in Sollozzo's position, neither will Sollozzo.

So "The hunted one" comment was technically true but Sollozzo was just playing for time, determined to kill Vito and not overly concerned about his chances of surviving a fight with the Corleone Family. Absent Michael's interventions Sollozzo probably would have gotten to Vito sooner rather than later. Sollozzo was a very committed individual..