Hello,
Re: Indirect + Suppression Fire -- No; Indirect and Suppression Fire are different attack types. They cannot be combined.
Re: Missed shots -- A missed attack always means a scatter with indirect fire. Resolve each grenade individually, and enjoy the show.
Re: Hit shots and MoS -- Each Grenade attack is resolved separately. Because the attack is Area-Effect, however, your MoS is always 0, per the damage resolution rules. Each grenade, however, is resolved individually. So, if you hit with a three-grenade burst, you resolve three successful grenade attacks with an MoS of 0.
Thank you,
- Herbert Beas
BattleTech
Catalyst Game Labs