Yes, I agree with the comments of others @Dauntedbydating. When someone that doesn't know you well (less than 5 dates, say) says things like 'I can see myself settling down with you' or 'I feel like I can trust you with everything' or start making plans for a holiday, that just seems crazy to me, as they don't know me. It just makes me smirk and go 'yeah, right' in my head, or thinking 'well, he's trying to get me to bed'. It's a little different if you are seeing someone who was previously a friend, of course.
Having said that, when I was fresh post break-up, I did fall for lines like that a bit, maybe because I wanted to feel wanted/needed again.
It doesn't sound like you lovebombed your date. It's nice when a man says nice things after sex. Was that the lady that was a bit hard work to get a 2nd date with?
About 'treat them mean, keep them keen...' Ufff, I think in my case it may be a bit of truth to it both ways. Not to sound like a run a harem, but there are a couple of guys that text me every single day to say they're thinking about me etc. They're sound enough but I don't see them as viable, so sometimes I reply, sometimes I don't reply all day. It only seems to encourage them!! I've also noticed that if I reply to someone immediately due to my keenness, over time they take me for granted a bit.
Then my 2 more serious prospects. One of the guys I've been on 5ish dates with and he will often reply back immediately, I'll know that he'll text me every day at some point, and have no anxiety about it. It's relaxed, nice and organic, and if he ever started not replying all day etc, it would go against him. It wouldn't make me want him more. He's getting it exactly right in terms of seeming reliable and dependable and open, but not needy/ obsessive.
The other one, the one I really want, is more sporadic. He might not message me for days or 4-5 hours and when he isn't messaging me, I think about him, and I think 'what could he possibly be doing that's more important? Is he not thinking about me as much as I think about me?' There's a bit of a cycle of anxious longing and then that sweet high when his name pops up on my screen. There's no predictability to him (apart from knowing he will message eventually if I leave him be) and it's making me think about him a lot more than I'd like. There's times when he messages a lot all day long and I think 'yup, I have him hooked' but then the next day, not a peep, and he's keeping me guessing again. But we haven't even kissed yet so it's not wrong to be a bit more detached.
What's my point? Communication content and frequency needs to be appropriate for stage of relationship.
I suppose if you know the other person is really into you TTM KTK can work - but why play games? I wouldn't recommend it as a strategy if you're seriously interested in someone though. Just don't reply to them straight away all day long/ write extremely long emotional messages/ say things that are too advanced for an early relationship stage. Don't clear your entire schedule and start talking about meeting your parents, or that you'll change your entire wardrobe because they like goths. But also seeming too unavailable will just make them think you aren't interested. It's a delicate balance to strike.