1.This たるis an old style, and this speaker tries to say,過ぎたるは及ばざるがごとし that is a proverb. It means, too much is the same as too little. 2. I'm wondering if it is a matter of me just because I'm too fussy? No I don't think so. (I think her line is unusual) 3. This expression is specific one that is used by special shops like "convenience stores" or "family restaurant". But I don't understand what this "ほう” actually means, because I don't like this expression. Generally speaking, when you want to avoid saying directly, you'd better use ほう. For example, when you explain a direction to somebody, you can say あっちorあちら. But when you want to say a bit vaguely, you can say あっちのほうorあちらのほう. I think this ほうis also used in that way. 4.Normally 口にする means that you take a little bit of food, but also used as "say" 5.This expression is also one of my dislikes. You should say よろしいですかor いいですか. And this expression, which was created by those store people, tries to say more politely. It is strange. So you shouldn't use it in a normal situation. 6. Yes, they must do.( The speaker is doubtfully assuming of the person's thinking, such as )"you can't say it is different, eh?" Hope it helps.