If this is your friend, and he that convinced he will "get rich" from this then there's really nothing you CAN do. You've obviously done your best to explain the situation to him, but he's been caught up in their sales pitch, and that's more convincing to him.
I worked in sales for many years, and the answers he gives you (the one about not needing to know the details of how your smartphone works is a classic variation of typical objection-handling that salespeople are taught) proves that he has been sucked in by their scheme.
At this stage, all you're going to do is ruin your friendship with him if you continue to press the matter, because he has made it clear he can't be convinced that this is anything other than legitimate. The reality is, he is probably in too deep at this stage to just walk away from it, so he has to convince himself that he made a wise choice.
Schemes like this use a "scarcity" approach (there's only so much to go around, and if you don't get yours now then someone else will get it) coupled with ego-boosting (boy, Mr. Prospect, this is such a great opportunity, and you're one of only a few who are sophisticated enough to understand and take advantage of it) to get people to lower their guard and not ask a whole lot of probing questions.
Nobody wants to feel stupid, and they don't want others to think they're stupid, so these schemes will present the information in such a way that ordinarily prudent questions come across as sounding dumb, making the questioner seem not so smart. Rather than walking away from it, peoples' pride will sometimes make them double down on it, and they'll just go along with it to come across as though they get it, even when they really don't.
The small payouts at early stages are a classic sign of a Ponzi scheme. Your friend will never listen to you as long as those little checks continue to come in, because to him they're absolute proof he's right and you're wrong. It's those checks (or payouts, however they're doing it) that will make him step up his efforts to recruit other people into the scheme or, worse yet, invest more of his own money into this.
Keep in mind that in the end, you really have no power to do anything in this situation other than be his friend and try to use gentle persuasion. He's already made it clear that he isn't going to listen to your explanations about why this is a scam, for a couple reasons. First (and probably greatest), it would be an admission that he's dumb, or at least not as smart as you, and who wants that? Second, he continues to get little checks that reinforce the fact this must be "real", or why else would he be getting this money? Third, he has already demonstrated his commitment to this by quitting his job, so from his point of view, this has become an all-or-nothing ticket to wealth.
The bottom line is, these schemes work because the sales pitch is powerful enough to overcome ordinary logic for people who think there just has to be an easy way to Easy Street.
All you can do is just be there as his friend and hope that he sees the light before the damage (to himself and anyone else) gets too great. You can't stop him from what he's doing any more than you can stop the sun from rising as long the message (and checks) he's getting from other people keep him convinced he's on the right path.
After reading the comments posted in this thread, I do want to amend my statements, because many good points have been raised here. You obviously can't just sit by and do nothing while your friend talks others into taking the same (or worse) risks that he is. That's not morally right by any measure
At the same time however, be VERY careful about how you go about this. Your friend, as you stated, sounds pretty much like he's all in with this scheme, so there's definitely going to be some serious emotional commitment to it on his part as well. Anyone and everything that threatens what he sees as his ticket to Easy Street could easily become a target when this all comes crashing down, as it inevitably will. You could very well be the cause of that in his eyes, especially if he knows you've been discouraging people from buying into this nightmare.
People are NOT rational creatures when it comes to money losses. It's called "sunken costs", where they'll continue to chase their losses on the rationale they'll make up for it if they just don't give up. The more your friend committed to this, the worse his anxieties about losing, so he'll do whatever he has to in order to save his position. This is what gamblers do and why the house does so well for itself.
Some have suggested making anonymous flyers or other means of communicating that don't expose you as the person spreading the message, and that's one suggestion. However, the problem with this is that since the receiver has no idea who sent the message, they're not likely to give it the kind of credibility or notice that they would to something passed to them by a person they know and trust, and your anonymous message will have little weight in the face of the persuasive pitch that got your friend to commit his own money (and future).
Another problem, as you've noted, is that you don't travel in the same circles as the people he's likely to recruit, so how would you go about warning them? How would they view their first contact with you when it comes with a message not to trust what someone else they already know is about to tell them? Would they write it off as someone who's butty? Hard to tell.
Another huge ploy of these schemes is that they tend to preemptively strike at what you propose doing -- that is, warning people to stay away. They do this by projecting the people giving the warnings as losers who didn't see the opportunity for themselves and now want to keep others away from their own financial success. They'll portray you as someone who isn't smart enough to see this "huge opportunity", and since you can't understand it, you don't think anyone else does either. They'll point out that if you were so good with finances, why aren't you already successful?
These guys are very good, and they have an answer for every objection you can raise, whether its to them or to someone else. They've spent a long time honing their message, which makes it difficult for anyone to say something persuasive enough to sway others away from being duped. This is a hard path, no doubt.
I hope you are able to warn others away. Just be aware that it may come at a cost to you as well, and be prepared for what that might be.
I hope this helps.