Re: Sunnah Way…
Brother, I assure you that no one consider Eid-e-Milad-ul-Nabi as fard. All perform Eid-e-Milad-ul-Nabi as remembrance and anniversary of Prophet (SAW) birth, considering that celebration as good deed, no more and no less. The most important thing about Eid-e-Milad-ul-Nabi is that people celebrate it because they love Prophet (SAW) and thus show their feelings for the day Allah gifted Prophet (SAW) to this world. As for rewards (Ajr), that is secondary for people who perform this celebration due to love of Prophet (SAW). Those who think of rewards, they believe that celebrating Eid-e-Milad-ul-Nabi would make Allah happy too, and thus they believe (actually hope) that there would be Ajr for this celebration as one believes that there would be ajr for any performed deed one considers good.
Same believe is about Ashura when Muslims, not considering fard but due to inner feelings, show grieves on inflicted atrocities that Prophet (SAW) family suffered at Karbala, and thus by doing so they try to join in the grief of Prophet (SAW) in front of Allah. As for matam, I believe no Shia do matam considering it as fard, rather do it considering it as remembrance of pain and suffering on anniversary of atrocities inflicted on family of Prophet (SAW).
Actually, Islam promotes remembrance and anniversaries. Haj is remembrance and anniversary of prayer that Adam (AS) did along with Hawa (AS) for forgiveness at Arafat (where they first met and recognised each other on earth). Allah made Hajis to run between Safa and Marwa and thus inflict pain of running on oneself as remembrance of pain and suffering at anniversary of what Bibi Hajra (AS) suffered while looking/searching for water for Ismail (AS). Hitting Shaitan with stones and Sacrifice of animal during Haj is also remembrance and anniversary of Ibrahim (AS) act. And so on.
As for rewards, it is up to Allah who is giver of all rewards (or no rewards) for any acts, be they fard, sunnah, nafil, or perceived good deeds, be that deed is remembering and celebrating Prophet (SAW) birthday, giving food to hungry or financial help to poor.