Okay everyone, I've had a long think about what is making me uncomfortable and it is this:
It unnerves me how he can change from one extreme to another. How he can be all cuddly and hand-holdy one minute and then ignore me for days. It feels almost-cruel. If I understood why he switched like this, I would get over it.
Paying for dinner, pretending to be a boyfriend. ... there's a market for it.
Why though? My FB knows he's going to get sex so why does he still add all the flowery borderline-romance?
have more than one so you're not becoming overly bonded with one person
Yep. I'm working on that.
Of course you don't generally have strong feelings for people you can stay casual with
How do people in 'casual relationships' generally feel toward each other?
I think your FB is in the same category as me
You think he wants a relationship? How so? He's hot and cold with me.
Wow Fairylea those are some pretty fucked-up signals he was sending. Do you think he enjoyed the mind-fuck? Got off on it?
If that disturbs her emotional equilibrium in this set up
You nailed it. I enjoy his behaviour (it's flattering) but I find it hard to reconcile with the view that we're just friends fucking.
Snuggling on the sofa, holding hands, chatting about work life etc are equally as a compatible with a friendship
I don't snuggle or hand-hold with my other friends. 
beaglesaresweet your post has produced a kind-of lightbulb moment for me. You reckon he does all this 'sweet' stuff because it makes HIM feel better about the untraditional setup of fuckbuddyship?