You can't rely on speed for more than 3/4 of the entire level, and you can't even dodge while being in the swamp, so don't worry about using heavy armour that puts you above half the weight limit.
Also, beware of the Black Phantom NPC with the Meat Cleaver on the swamp, he isn't affected by the effects from the swamp and can easily run and dodge.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
