I would install a catch can on any forced induction engine (turbo or SC) no matter if it was DI or not.The 3.7 is a port injected engine and does not require any catch can. There is generally only an issue with DI engines needing a catch can.
I change oil every 5000 miles. I empty my JLT catch can 1/2 way through an oil change. You really should be opening the hood more often then just at oil change time.