Since he is still around, your best bet is to put catnip out where he's been seen, and watch for him to slow down for that (in your car).
Once he's spotted and slowed down by catnip, set a trap and don't leave it! (And use your call for him-whatever it is, to keep him around). Use tasty macarel like previous advise, or cooked warm chicken (I use the chicken legs, precooked at the grocery store for difficult catches) tied to the back of the trap with wire like bread ties so he can't pull the bone of meat down but just pull meat off of it, (and with this, he is more likely to step on trigger). Don't use a small Tomahawk! (sp?) Big cats trigger them accidently with their backs, freak out, back out, and are forever trap shy. Use a big trap for a big boy! Always stay with your trap, you don't want to waste time on skunks etc because if he sees them trapped, he will be trap shy, and you may have to clean out a stinky trap (no cat will go in a stinky trap unless it's stinky from food). You don't want males peeing on it etc. So watch it so you can jump out of you car when the wrong creature is going in (use flashlight)
I worry that if and when you do get him back, it will be the same howling problem, assuming he's nuetered, he may never "get over" this part of his personality but you could at least get him tested and keep him in or in an enclosure if he positive fiv or luek.
What you went through was horrendous and i am glad that neither of your cats died or were lost! (and of course you!).
I wonder if someone is feeding him and if so, you could tell them not to for a day and put a trap on whatever they are feeding him on (porch etc), otherwise, what the heck is he eating? If he's eating mice and birds, he's probably full of worms and could use a few doses of strongid. Tom cats benefit from deworming for obvious reasons!
Anyway keep us posted, are there animals that eat cats in your area? We have fisher cats that eat cats and I get so angry at people that let their cats out and then wonder where they could be (food for fishers - "hello?!!!!!!!!"