Ok... so how do I escape the sewers?

I'm at the point where all those little spiders keep exploding on me and kicking my ass. I throw a bubble down, kill them, they keep coming. I eventually die.
I throw bubbles down in a path towards the end of the corridor, I eventually run out of energy and die.
Am I suppose to actually do something?

You can use the time warp on them to do...something to them that makes them turn on themselves.

I dunno if it reverts them back to an earlier version of their evolution, causing them to not recognize eachother or whatever, but using the time shift on a few can easily dispatch quite a bit of them.

Well, I only have 1 bar of energy. Not like I can get very far. But oh well. I just ran past them trying to slow them down with the bubble. Got to the end, now I have 1 pt of health, no medkits, no energy.

restarting at a checkpoint refills your health

That's probably the hardest part of the game.

I died there for like half an hour.

What finally worked...

1.) Equip Valkyrie.
2.) Go to a corner immediately after opening the door (left or right).
3.) Shoot a dead lock at the ground.
4.) Turn (LB) one of the spiders in front of you, shoot all the ones behind you, start charging up a second deadlock.
5.) As soon as it drops, run for the middle pipe and drop the dead lock behind you. The spiders will all attack the one spider you used LB on and will give you enough time to get to the door.
6.) once you drop the dead lock, run like hell down the hall. There will be another group coming in front of you after you shoot the first one, so take care not to miss.
7.) Drop the last deadlock behind you after you kill the second wave, and run for the ladder.

It's easily the hardest part of the game to be honest. After that point, you start getting upgrades out the ass to where you just destroy things.

BTW, how far into the game am I? Percentage wise, I mean.

jeez that was hard, just got through it

It helps to use the TMD on the pods before you open the door. You can't kill them all but it reduces the number that come after you. There are some in pipes on the sides that are easier to get by jumping.

I have tried all these suggestions. I die before I get to the corner sometimes. Is there a God mode on this game so I can get past this? It is getting real boring playing it over and over.
Also, is there a way to change the games difficulty level in midgame??