Customized Code on Free, Open Source Software

Hi, I'm looking for effective filtering software for my laptop. Specifically, I would like to block all porn and 'adult' websites. I have consistently been disappointed with most available software, due to cost, ineffectiveness, and a large footprint that slows down or messes up normal web browsing. I am currently using a free, open source app called Self Control. [login to view URL] I like Self Control because it can't be overridden or deleted and it has a small footprint as far as I can tell. Its almost perfect. However, the app was designed for social media and time wasters rather than filtering. For example, the maximum block time is 1 day. I was hoping to have you customize the code to make it better. Specifically, I would like to change the software from a time based block to password blocked. I would like the app to block all sites on the blacklist unless a password is entered to override the software. I am open to some suggestions on how to accomplish my goal if this is not the best way to solve the problem; I am not a coding expert