Yes, it's inappropriate, and I can understand it making you uncomfortable. But as you say he wasn't and isn't being aggressive about it, it really doesn't seem to me to be a big deal- he was just trying it on. You didn't say if his propositioning was polite or crass, so to me that would be a factor. People meet their future partners in all sorts of unanticipated situations, there's nothing innately wrong with a host and guest being attracted to each other, and someone has to indicate that attraction at some point. I probably would have responded something like "I'm flattered, but no" and then just moved on, rather than letting it make me feel uncomfortable going forward (but, of course it depends on how he worded the proposition).
There is another female host who posts here often who had a similar situation, although the proposition was verbal. It made her quite uncomfortable as well, and after he checked out the following day, she messaged him and let her know how such things make a female host feel and that it was inappropriate. He answered back with a sincere apology, he really hadn't meant any harm by it, but acknowledged that he shouldn't have done that and thanked her for setting him straight.
As far as walking the dog, that was presumptuous, but I don't see that any harm was intended. Sounds to me like this guy just isn't that savvy about boundaries- sometimes people just need to be gently educated as to what is appropriate and what is not.
If he was being aggressive, my take would be different, but it doesn't sound like he is- just somewhat clueless.
@Kathi6