Looking for some basic pointers for building a new elasticsearch cluster

Looking to deploy a cluster that will consist of 2 physical servers running debian. Anticipating 1500EPS and need about 3 months retention. Each server will have about 70TB of space
Walk me through the basics, I understand that a minimum of 3 nodes is suggested to avoid split brain. Can install more than 1 node on a physical server? or is this a bad idea and I need more hardware?
A shard hold an index and an index can live across multiple shards. can a shard hold multiple indexes?