Push the jump key and crawl key at the same time or the jump key first and while in the air then the crawl key. The game will hack your char a bit but you are actually jumping higher which also means you can jump longer.
Consider the ghost house, why waste time falling down through the stairs to find your way back up again? You can simply jump a 1/10 of a sec before you go through the floor and not fall down at all
There is nothing worth the time down there anyway... Also in the museum jumping on to the flying dino bird to collect 100 dollars is a lot easier and jumping across the waterhole when you go into that filfy nosf in the sewer spreading the plague is faster and easier than the much much well a little longer way around ^^Also makes it easier to jump onto the open trashcontainers around town where you can wonder why you cant fall into big open hole
but heck there are a lot more funny bugs around than that though less usefull.