can you lock on in this game?

Use L2 to lock on to enemies. (just don't use R2 after that, unless you want to throw the weapon at the enemy.)

I only ever really used locking when using firearms though. As for blocking, it's not so much a timing issue. You can hit triangle and Murphy goes into block mode, and it will keep blocking as long as you keep it pressed. BUT you do have to be facing the enemy, which locking will help you to do. Although if you just keep the block button pressed the whole time, the enemy will eventually break your weapon.

If you don't want to fight the enemies, there are a lot of places to run to, and a lot of them will actually stop following you after a while. The exception are the Screamers, who can tag behind you quite a ways. But if you go into a building and wait there a while, you should be safe after.

I can't quite confirm this, because it seems kind of random. Sometimes they seem to hang out there forever until you come out, although more often than not, they just disappear when you come out, at least they did for me.
I'm talking for outside the town here. It's a bit different in dungeons, but shutting doors behind enemies, or shutting them into a room after luring them in works pretty nice if you're not up to killing them.

For fighting enemies though, I found that blocking helped quite a lot, once you get to know the patterns of the enemies. When you learn what animation means they're striking, it's easy to block, and then when you see an opening, just bash away. This works good on the weeping bats. For the screamers, I usually barge in there and hit them so they can't even do anything. But if you miss, they back up. Hit block, and keep it pressed because then they're usually coming in with a three hitter. Then strike. I use the same strategy for the prisoner minions, but they're a bit easier. They are tougher, but not as agile as the screamers. But those guys, if you even step away just a little, they never really do anything. They FOLLOW you, but they just keep taunting and dancing around. You have to get real close to provoke them. However, again this is outside town; in the dungeons, they're much more aggressive.
The doll enemies I never really understood, I just hacked away at the mannequins that give them life, and hoped I had enough time to destroy it before the spirit got to me.
Blocking is pretty much my key, and I never used lock. It's not too hard to position yourself head on with the enemies and keep it that way while fighting. But it does get tougher if there are more than one. Firearms are good then if you're in a dungeon, otherwise I just run off.

I have no real strategy for the prisoner juggernauts. Use shotgun attacks on them; close range will make sure they fall in two shots. Fortunately, most of the time you fight those, you should probably have more than enough shotgun ammo on you. Taking them on melee works alright too though, just beware the rush attack.