I would suggest that you load up the Hellcat single patrol.
You have a Balao so you have radar, that will help in finding targets and tracking them. Also it will go to 600 feet, always a good thing.
Set your options up with no duds, map contact on, you want to learn patrolling and finding and tracking contacts first.
Limited fuel and batteries as they really won't play a part in the mission.
Forget about the star in the Sea of Japan. Just plot a course to the Luzon Strait and use that as a Tutorial. You can use very high time compression till you get close to the Philippines than slow down to about 256 to 512 TC. Save the game at this point so you don't have to do it all over again, you can start from the save and try different things.
Set your speed at 10 knots for transit and patrolling. Dive only when necessary to avoid planes or set up an attack, slow speed only to save batteries and fuel. Use TC of 128 in the day to 256 at night.
You can find contacts anywhere in the Luzon St. and down towards Manila
Here is a search pattern I use but it's different every time. There are planes in the strait so I move a little south or west.
Radar can see 20 Nm. either side of your boat so don't get too close to shore.
The shipping lane map will give you many good places to patrol and you can see where ships are starting from, where they are going and what routes the may take. If you don't have one there is a download around here somewhere. This is information real captains had, so I use it.
Dinner time so I'll take this up later.
Magic