Running away in the swamp almost always ends badly. You need to stand still and kill whatever you have agro'd. At that point in the game you should be able to 1 shot skele (depending your weapon) and the abom is easily dodged for a melee kill, no need to try get a portal down to escape.

The first 2 zones teach you bad habits because nothing really punishes you so players get to the swamp and think running around half a biome shooting arrows is the solution to almost everything, it isn't.

Speed run is about 8 real life hours last I looked btw.