His first three points: "Spread risk through multiple projects and multiple partners", "Do as much as possible myself" and "Question everything all the time" sound like a perfect recipe for pissed-off cofounders.
I don't think I'd want to be this guy's partner if I knew that (a) he'd only be working part-time, and when he felt like it (b) he'd insist on doing everything himself while he was around and (c) he'd probably spend most of the time that he was around questioning all my decisions.
I currently have two co-founders on two different projects, and then three projects I am doing myself (with lots of ideas bounced off my wife and other entrepreneurs).
One of my co-founders I previously founded a different company with that was sold to a public company. He is also currently running another business. So he knows the modus operandi pretty well.
My other co-founder also runs another business. So there really isn't any time resentment there either.
In answer to your points a-c:
(a) I work on all the projects all the time, at least to the extent that I am thinking about them and coming up with ideas continuously. In other words, I don't silo them in my head. While they are quite distinct, they all are Web based, so there is significant useful overlap.
It's not when I feel like either. We schedule specific times to meet, discuss, and work as needed.
(b) I don't insist on doing everything myself, but I do insist on knowing the details of everything inside and out. That being said, on all my projects (right now) I am the only (highly) technical person, so I naturally do all of that stuff myself, e.g. coding/sysadmin/etc.
(c) I do question everything, but all the projects are much off better for it.
I don't think I'd want to be this guy's partner if I knew that (a) he'd only be working part-time, and when he felt like it (b) he'd insist on doing everything himself while he was around and (c) he'd probably spend most of the time that he was around questioning all my decisions.