The word viharati has the general sense of “dwells, stays, abides” but is used in many idiomatic ways. In Pali EBTs, it commonly means “meditate”. For example, the nava anupubbavihāra are nine successive meditation states. Thus while most translators use “dwellings” or something similar in such contexts, I prefer to translate it more explicitly as “meditation”.
How do we know that it refers specifically to meditation? Context! It says bahula “frequently, often, usually”, a phrase it then repeats in the next line with reference to jhāna. Since it’s asking about how someone gets enlightened, clearly it isn’t talking about the monastery that someone stays at!
To conclude: the phrase here doesn’t mean a bhikkhu who resides in Dhamma, it means one who frequently meditates.
Dhamma-vinaya is a dvanda compound, and it refers to the theory and practice of the Buddha’s teaching. Svākkhāta means "well (su) explained*. So the phrase means “well-explained teaching and training”(or “teaching and practice”).
It’s used when the Buddha wants to contrast with other spiritual systems that are poorly taught by their founders.
So no, “investigation of Dhamma” is not correct.