I quite agree with you Ep.3 felt like shipping fuel for Mami/Madoka and even if it is infatuation no one ever says that it can't grow into love.
Regarding the question of Mami romance quickness, I feel that it is just right. Out of all the cast, Mami is the one who
wants companionship more, she's really lonely.
And now my two cents on the order of romance option that will be available. Feel free to skip it, its just something I thought about while reading your VN
Looking back in hindsight the order of prominence of the cast in the anime seems to me also would fit the order where they can romance if it is a typical VN. Mami is the easiest she can be considered to be in a recruitment for a partner before the anime even started
. Evidence Drama CD 3.
Sayaka would be next since she's already close to Madoka. Madoka just needs to open Sayaka's eyes to possibilities. Next, would be Kyouko, she may be tsundere about it but she's very quick to care. The last and the hardest funnily enough would be Homura.
Many would argue that Homura should be the easiest to romance. Homura might already be in love with Madoka at this point in time, and regardless of what position anyone interpret their relationship (platonic or romantic) - Madoka is the most important person in Homura's heart. That unfortunately does not make Homura any easier to romance.
Homura may
need companionship more considering she's in
groundhog loop hell mode but at this point Homura is probably the hardest to romance because unlike Mami she doesn't want companionship. What Homura wants is for Madoka to be safe and happy and have already concluded that she can't provide that being destined to be a witch and all.
Thus, I have concluded that to romance Homura one must know everything about the puella magi - the lich, inevitable witchification and perhaps even her groundhog looping or Homura will feel that she's taking advantage of Madoka or make Madoka unhappy or worse endangering her. Thus, it is fitting that Homura would be the hardest person to romance , Then, there's Walpurgisnacht coming...
And now its time for me to stop rambling ...