People overdo “into” all of the time. Sometimes “in” and “to” are just friendly neighbors who happen to coexist in a simple platonic relationship. “Into” is a preposition most often answering a “where” question. Where did I put my wallet? Into my pocket. Where did you get that camo? When I went into an intense kickball league. (ooh, metaphorical “where” – tricky).
“In to,” on the other hand, are just two words in a sentence. He went in to see what happened. She kicked it in to score a goal.
And yes, the saying “into” as in a hobby (“really into stamp collecting”) or a love interest (“really into grammarians”) is correctly written as one word.
Got it? Happy writing!