About that Ryu and Tamao thing...I find that he is MUCH more mature at 25, and I also think EVERYONE but Hana knows about Anna's and Yoh's situation of wutever they might doing, and most likely knows that Tamao is trying to replace Anna for Hana's sake, so Ryu as usual would always have to be forced to do hard tasks and obey them like he did for Anna as a cover up in front of Hana. In all, I'm saying that Ryu and Tamao have absolutely no connection, as Tamao still loves Yoh and respects Anna and for their sake, must impersonate Anna and take care of Hana instead of chasing her dream to be a pop idol. As for Ryu, he only wants to be on the road and just wants to serve under Yoh and Anna as the chef of Funbari Onsen and has grown over the unsuccessful personality of asking out every single girl he first sees, although I do believe he is still searching for a love life but is more considerate about everyone and certainly knows that Tamao has no room for him (and is also too young).
As for the most likely candidate for Chocolove, I believe any argument on that topic to be pointless because even we wouldn't know what to think because of how there is absolutely no evidence of him ever even showing any type of friendship towards any of the girls, he's only commented about Pirika of how she has a slow sense of humor and never shows any type of positive attitude towards that, as in I don't believe he'd like her because she's the only one who laughs at his jokes. He simply just never shows any evidence of any type of interest towards the girls.
If you were simply asking of possible candidates, I can say who couldn't be, and that would be Tamao as she still and only loves Yoh and seems satisfied if she were to always stay as a single pop idol. As for candidates, it'd be Pirika because of how, as I said before, he might like her for being the only one that laughs at his jokes, and if you were including the anime, that one singing girl of relief from darkness could be a candidate also because of how she was freed from not being able to trust anyone by Choco.