Solomon died in the alley? Right after that one fight. He met Amshel there, but Amshel didn't even need to do anything, before Solomon turned into stone. I think that was a pretty clear scene. Maybe Diva's chevaliers every now and then were saved from that fate, like James, but it required some vats, replacement bodyparts, Diva's blood, and other things not available without Amshel and Diva's blessing. I doubt Solomon received such treatment after his betrayal.
Nathan said he was Diva's chevalier just before Saya killed him. Of course he could have lied, but I see no reason for that. Why would a man lie about such things just before he got killed willingly?