Egon being the mentor of the new team makes even more sense than it initially appears since he clearly demonstrated massivePapa Wolf tendencies in the original show.
While Garrett's claustrophobia is a fairly straight forward fear on the surface, it actually has a deeper layer to it; namely, that Garrett is afraid of being helpless. This is supported by "In Your Dreams", where the thing that really freaks Garrett out in his dream isn't that he's out of his wheelchair, it's that he can't defend himself and there's no chance of making it stop, unlike most situations when he falls out of his wheelchair where either he can retrieve it himself or there's someone to help him.
In "The Undead Bride", Eduardo seems to be displaying stupidity when he fires at the mirror. However, keep in mind that not that long before that, he dealt with demons that dragged him into their world through a portal in a mirror. He must've assumed the bride's powers worked in a similar way, and he'd be firing into wherever she came from. With the information available to him at that point, his logic isn't unfounded.
It might seem odd that Egon gets so worried about getting old at only thirty-nine, but as Janine says only two episodes later, he's having a mid-life crisis. He just happened to have his first-likely a result of subconsciously dreading his upcoming fortieth birthday.
On a related note, the reason Egon has such a (relatively) easier time snapping out of it, compared to the other three, is because his was based on fear, so he just needed a bit of rationality to dissuade that fear. The others' were based on arrogance, so they needed to learn they're not invincible-a lesson that can only really be learned the hard way.
