Maine Coon not like other cats I've had........

My Fluffs adopted us w/i a day of losing our 18yo Baby Boy who we had to put down. This cat had been around for several years and very skittish, but suddenly at our door. We've had him for 3.5 yrs now and it's been a rocky road. At first he wouldn't let us hold or touch him much, and was very traumatized by having to fend for himself for so long after being abandoned by his previous owners. He's still extremely paranoid when eating, will paw at me, rub me w his head, anything to get me to stay w him when he eats, always looking over his shoulder to make sure I'm there. He will let us hold him while he looks out the upstairs windows and I can now get close to his neck/face and talk to him and kiss him but he's like others say, definitely not a lap cat. He growls when the doorbell rings, runs and hides until the leave if someone comes in; he gets in fights protecting his turf; not a good house cat sine on on for so long. He doesn't like other cats and stays up many nites ckg the windows for signs of interlopers; growls and spits when other cats r present.