@McLXIX Coincidence or not, the father has entered the scene for other twins too. As a result, as much it may be some sign, it's a weak sign imo.
As for the signs of attraction, Fuutaro has been more romantic sensitive because of Nino, yes. But I take it it's less Nino-only but more that he notices at least two of the Quints is in love with him (the other being Miku). As someone who has claimed times before of his lack of understanding girls and romance, he's taking the best approach he knows of: from the book. But even he realizes he needs to stop that. Hence point 1 is null.
Point 2, he is under the assumption that Nino is in love with him; as mentioned above, he's trying to get the grasp of romantic notions. Of course he is going to be bothered by the change in tone, as if someone had told him a lie. He's using the "lessons" as a guideline because he's still learning the ropes, so him using them is like using formulas from a textbook when doing some problem solving. Point 3 hence does not hold ground.
We are much aware that Fuutaro is taking notice of the Quints beyond being just girls, especially for those he has become aware because of confessions. Wouldn't you feel taken aback when a beautiful/handsome model gives you the "don't touch me" response?
Point 5 is you taking a coincidence for a fact. He thought of the Quints, and thought about giving flowers. However, as he says in the chapter, he doesn't want to be present. Therefore, he gives it to whoever he meets next, which happens to be Nino. It's a nice notion that he at least sees Nino approachable enough, but I don't think it was in his mind to appeal to her "you liked your mother" side.
Fuutaro may be blunt, and he's trying to learn romantic "language," but he is still clueless about a lot of things. If anything in honesty, I don't find his question of "Didn't you actually come to hate me" to be anything more than an honest question he never had the chance to ask. He's seeing Nino's love for him out of analysis, nothing personal yet, which is why he asks about her when she "come to hate him again" because of his past trauma of being hated by her. It bites her in the ass that she disregards how harsh she had been. I also wish to add that seeing his response in a black-white way (reject = hate, all other = love) is terrible, since you can consider that any person would not like to be hated, especially with Fuutaro who wants to get along with all the Quints, knowing in most cases they want to operate together.
Undeniably his small blush may be a hint that he seeks more than "be friendly," but as we may know, if he aint used to the affection, he's going to blush. It makes him out to being a bit green, but he is. He hasn't experienced romance as much. But to treat it in absolutes, once again, just causes exaggerations.
Placed this ins a separate response for the good sake of length.