Clearly if your painting or photography or whatever is a hobby....that cannot be construed as 'working' on a sosbud. If you intend to sell your hobby product later in a foreign country, out of Indonesia, that also isn't a crime.
Only you will know what evidence he has, if you have not complied with Law, to have you in trouble with Immigration.
If you are confident you have sufficient evidence that this guy is a predator...of course you must trust the police...but you must be clear that what you believe as harassment, threats and, in particular, blackmail, are evidenced. Just saying you belief he was doing that will not be sufficient and they will probably not wish to believe you.
It might be better if you can copy all evidence and show this guy you mean business and will report him to the police....hopefully he'll get your message and move on.