Leo's hair-do is NOT coming back in style, and he is currently making a living as a (new!) shoe salesman & sock strength tester.

😉

He's the top secret billionaire funding the box :p

He installes invisible fences for dogs.

I believe Leo is alive and not too well.

Leo is actually going to perform at the Roadhouse. It's an Avant Garde, spoken word piece entitled new shoes. 

Members of the audience are given umbrellas so they avoid any spittle. 

I'd assume the spider bit him and he died. The fact Bobby and Shelly got married sorta supports that cause there's no way he would allow Shelly a divorce. 

Yes, there really was no escape for Leo from that trap. He couldn't even attempt to escape without releasing the tarantula. There are many from the earlier series whose fates will never be known. No one talks about them in TP any more.

Like Hank, he died at some point, one way or another. Well before he tried to kill her at the mill, Shelly realized what a bad marriage she was in.

He did not die from spider bites(Tarantulas ha no poison).

He was shot dead according to The Final Dossier.

So the question is: Who shot him dead?

Mr C ?

Leo gets electrified by W.Earle several times in S.01. Gotta be good old Windom that shot him full of bullets too.

Maybe it was Bobby /Shelly 

For some reason I was always under the impression that it was Hank that shot him.

I still like the idea of it being Catherine.  Just seems like something she would do.  Why?  Because he sucked and she can.  She did afterall, untie and pull his wife from the fire. No matter what Albert said in TFD, I still vote for Catherine.