That sounds like a decent reason to get the Drake Sword, you know, seeing as videos take a
ton of hard drive space.
I'll put it in "watch later"
(Too addicted to Trigun to watch anything else right now)
Edit. Watched it, finally.
The enemy with the weird looking heavy weapon that killed you is very tough. His name is Havel the Rock. His attacks will one hit you (with your current health and armor, anyway) and he has a lot of health. Right now, you don't have to fight him, but if you do decide to fight him, he'll drop a veeeeeeeeeerry nice item for you. I'll keep it a surprise
The lizard boss that you fought is a Taurus Demon. You'll need to fight him if you want to progress any further. There is no way to flee from him once you enter the fog (other than using a homeward bone to return to the last bonfire you visited with all your humanity and souls). You had the right idea on how to fight him in episode 4 before he jumped up the tower, you need to fight him the same way you started fighting the first boss (jump down and attack his head).
If you still plan on getting the drake sword you'll need a bow and you'll also need to increase your strength stat in order to wield the drake sword (16 strength if I remember right)
Also when people write "need humanity" they usually mean you should summon someone to help you, which requires you to be human, which requires you to restore your humanity at a bonfire with humanity (meaning the number at the top left corner of the screen, not the item). Thought I'd add that just in case you were wondering.