Are you using glued fittings for the trap under the sink or are you using the slip joint kind? You can use slip joint so you can adjust the angles.
Yes, you can point the trap where you want so long as it has sufficient space. It's probably better to aim it toward where you want it rather than having to use long sweeps. The more straight runs you have, the less obstruction & the easier it is to snake out. You can get P-trap with trap adapter (goes from the slip fit to the solvent weld type of PVC) as kits at big box stores. The slip fit isn't as sturdy as the solvent weld so I've found it is more likely to crush in when trying to use a cutter so it can be a pain if you're not used to working with it. Kitchen sinks usually have 1-1/2" drains so you could get that sized kit & expand up to 2" later in the run. I'm trying to figure out where your vent would be-- is it going to be in the wall?
Sounds like you got an awesome deal on the cast iron stuff! I take it you're running a separate water line & drain for the dishwasher? I know a lot of people put the dishwasher directly next to the sink & use the sink's drain. My family got a freestanding dishwasher that has to be pushed over to the sink, have an adapter attach to the faucet & hot water turned on at the sink. It then dumps everything into the sink when it drains. It's such a royal pain that we haven't actually run it in years. In retrospect, I wish we'd gotten a built-in & put in a small island to make up for the lost cabinet space.
Just to be clear, your sink is on the peninsula (like an island but attached to other cabinets) right?
Red line represents the drain path?
Is your vent for the sink going to be in the wall?
Frodo can probably tell you more about the vent length requirements because my brain is still in zombie mode right now.