No worries on the lengthy post, knowledge is king so never be afraid to ask questions. To answer your first question a 20 gal long tank will be fine just make sure you have plenty of hides for a smaller corn snake to help him feel secure. As far as temp goes just make sure you have a thermometer on both the hot and cold side of the tank. The hot side should be between 80-85 deg and the cold side should be in the low to mid 70's, you shouldn't need and fans for you corn snake enclosure.

The Enclosure humidity should be okay were it is at 20-30% because corn snakes don't need a lot of humidity unless they are getting ready to shed. When your snake is ready to shed what I like to do is take my snake cave like this on http://www.exo-terra.com/en/products/snake_cave.php and fill it with moist Sphagnum moss http://zoomed.com/db/products/EntryD...D=2&SearchID=5 until it shedsl. I do this with all my snakes and when they are in shed phase they hardly ever leave this rock.

To answer the personality question, corns snakes can be more mobile and twitchy than BP but all animals are different, you will occasionally find a BP that will have a cranky personality, it just happens. What I recommend doing is checking with some actual breeders online like http://bhb-reptiles.myshopify.com/co...ns/corn-snakes or http://www.lllreptile.com/catalog/54...-and-ratsnakes or checking on any breeders in Canada closer to where you live for shipping cost reasons. But what they can do for you is not only have a larger selection of paint jobs than a chain store but you can also contact them directly and tell them you are new to corn snakes and request they send you one of the calmer snakes in there collection. This is what I did with my first snake I bought from BHB and they were happy to oblige.

For you last question the rule of thumb is if they can fit there head through a gap then they can get the rest of there body through, so if you gap is bigger than there head you will want to try and fill it with something they cant push out. I wont lie corns are good at escaping so if there is a hole it will eventually find it, and cats would love to get at little snake if they get the chance, I know my cats will sit and watch me when I'm handling my snakes just waiting to see if I'll put them down for them to play with, of course I don't let them get close to me when I doing that for safety reasons.

I know you didn't ask but I wanted to touch on substrate real quick. As I'm sure you know there are several kinds of substrate, I typically use paper towels or Eco Carpet http://zoomed.com/db/products/EntryD...D=2&SearchID=5 they are both very easy to work with! Paper towels you just toss and add new the only drawback is they don't look the greatest if you care about that sort of thing. The Eco carpet looks nice and it's washable, I just recommend you buy 2 of them so you always have a clean one ready to go in when your cleaning you enclosure. I will say the carpet doesn't lay very flat at first but after a little while it will straighten out. The main reason I am bringing us substrate is because a lot of people recommend using Aspen Chips or Shredded Aspen for corn snakes which is fine for older snakes but it can cause issue with the smaller ones. I used Aspen bedding for my first corn snake and after a few months I noticed a slight swelling on one of his eyes and after a few days it was really swollen, it looked like a large clear bubble over his eye, I'll post a pic to show you what I'm talking about. What the Exotic Animal Vet said probably happened was the dust created by the wood chips can clog up there Nasolacrimal duct (tear duct) if it gets in there mouths. Snakes tear ducts drain into there mouths and the smaller baby corns have very small tear ducts that can clog very easily. Typically if this happens and it doesn't resolve itself quickly it can lead to blindness, eye rupture, and infection and typically the only way to fix the problem is to remove the eye altogether because the baby snakes are to small to clear the blockages without harming them worse than they were already. I just want to say that I'm not in any way trying to scare you but I just try to tell people what I've dealt with.

Well I hope this helps answer any questions and if you have anymore I will do my best to answer them.