A piggy should never be kept alone so finding him a friend should be your priority.
If you get the wrong piggy, a piggy with whom he isn’t compatible then yes he is going to be angry about that so this is why you need to go about getting him the right friend the right way.
You can keep the old cage and join it to the c&c but if you do that you must make sure that the cage is thoroughly cleaned and neutral. You cant allow them to meet within that cage though as your current piggy will see the current cage as his territory so won’t allow a new piggy into it (can be seen as a territory invasion and cause a fight) if you don’t go about introduction properly. Please read the bonding guides on how to introduce piggies.
Yes it is the pile of hay they will eat from. That is how it should be. You don’t want to use hay racks or any kind of holder as it removes their ability to freely forage in the hay, make tunnels and nests in it and play in it. A large pile of hay is their main source of enrichment and activity as well as their main source of food.
For other enrichment - tunnels, cardboard boxes with two doors cut in. Don’t use food bowls and instead hide their veg portion (one cup of veg per pig per day) and pellet portion (one tablespoon per pig per day) amongst the hay pile so they have to use their brains to find it.
Enrichment guide below
Enrichment Ideas for Guinea Pigs