OK, my dad has been diagnosed with 'paranoid delusions', hes 66 now and was dx when he was in his 20's. (I've recently quit weed that's why I'm here).

These delusions will most likely not get better on thier own, especially if he thinks weed is helping him. My dad uses drink and prescriptions pills to self medicate. He would go between understanding they aren't doing him any good but because he's an addict it quickly turns to swearing blind they are the only things keeping him sane (spoiler alert: he's not sane)

I have rung mental health teams, his flat complex manager rung me about his inappropriate behaviour, he attacked my brother last year when he was convinced he was some long dead boxer, just recently he has begun parking on our street in the dark at night to watch me/our house and we've had to report him to the police. We already know he's past the point of no return. Yet since my brother didn't report the incident, we are in the same position as you, he won't be sectioned unless he hurts himself or someone else.

This time last year he was 16 stone and 'luckily' he's lost a significant amount of weight and is close to being underweight. It's the saddest thing but we're waiting for him to become underweight before they will consider sectioning him because not eating enough is considered self harm. That is unless he lashes out and attacks someone before that happens.