Family member looking for more advice

Hello, at my wit's end and hoping someone might have advice. My brother in his 40s (likes living away from us, no immediate family of his own and small extended family only) seems to have (undiagnosed?) irrational paranoid delusions that are increasing, wide-ranging and affecting his life significantly. He is not getting work (despite trying) and it sounds like he is living in a nightmare that ranges from when he is coping with the beliefs and their impacts to (often) when it is problematic or all too much. He is unwilling to seek or accept help (which I gather is to be expected), even though he often asks me how to stop the things happening to him. I realize it is not a good idea to directly challenge his beliefs (including the one that I'm involved) and he also rejects suggestions to see a GP for something else. At the moment he still keeps in some contact over the phone (at best thinks I am misguided but with good intentions, but more often is mistrustful and rarely, has been upset enough to verbally threaten violence for not having the answers). If he needs to be an immediate physical danger to himself or others before he can be forced to accept some form of help/treatment, that doesn't seem to fit yet. Just hoping someone out there who has loved ones in similar situations or have been there themselves had any suggestions about what might work, so at least he can be in control of his own mental health again? Thank you for taking the time to read this and for any advice you might have, it is much appreciated.