Yes, he's been treating Bum like his mother since the earlier chapters.
But did sangwoo put sex toy in her mom but too?
Or its just his effection toward bum in person
No, Sangwoo did not dildo rape his mom (not that we know of anyway). He's not treating Bum like his mother in every moment however at times he has treated Bum like his mother. I think throughout most of this chapter he was treating Bum like his mother. He did the same in the begining of the series when Sangwoo told Bum he remind him of his mother.
Are sangwoo see bum as his mom substitue or something??