Be sure that you have things set the way you in the career. When you are in the base Captain's Office, to the left of the desk is a "file cabinet", and on top of it is a wooden civvy radio console. Click on that and you'll get the options for the career. This is modifiable for each career you might have running, and is separate from the one on the main menu, which is for Sub School, Single Missions and War Patrols (plus multi-player). The FotRSU mod by default has that set to "off", with the tickbox empty. But even with that set, the base FotRSU dud rate is lower than the stock game's setting. To get something closer to "realistic", you would have to use "650_LotsaDudz" from the "
AddInModzPak_v18" collection. If that's too many (and for me, it frustratingly is), then use the "650_MoreDudz" mod, which is more than "650_OriginalFOTRS_Dudz". The "MoreDudz" for me seems about right, usually. Use only one at a time, hence them all three having a "650_" designation.
FotRSU has CapnScurvy's "Medal Fix" in it already. The "Purple Heart" is similar in function to the "Philippines Campaign" medal, in that it is reserved for lower-scoring patrols that do OK, not for good patrols. Look closer at your Captain's Log, and you might see that you sank a Russian "neutral", or a hospital ship, or (horrors) a friendly. The Japanese were "famous" for putting Hospital ships in regular convoys, and would have the lights out on them. I have had more than one patrol ruined by hitting and sinking them, usually quite by accident with a "miss" on a different ship. I have also been fortunate in hitting them with "duds" before also... lol - The "neutral" and hospital ship are worth a 1x negative amount of renown, while a "friendly" will ding you 10x a negative amount. They will affect your "patrol rating" also, which is what the medals and other "awards" are based upon. With CapnScurvy's medal fix in the mod, you will find it a bit more difficult to get higher than the Navy Cross.