Hi Everyone!
Thank all of you SO much for responding so quickly and helping so much!
Here's the update on Moose so far... We made it through the night but it was a really rough night, he threw up all of the lamb and rice bland food that I was giving him to calm his tummy. He also had a little pepcid and canned pumpkin for his tummy upset. Moose had diarheaa throughout the night and into this morning. I have been force feeding him water and pedialyte to keep him from getting so dehydrated.
He ate a little more lamb and rice this morning, but also threw this up

It seems the poor little guy's tummy just isn't tolerating anything right now. I spoke with my vet again, as well as they owner of the pet food store that I had discussed Evo with. Both say that sometimes the wet Evo food just isn't recieved well and to try Moose on the dry Evo kibble.
Right now, I am boiling chicken and white rice and just giving him a little at a time and keeping him hydrated. He hasn't thrown up or had diarheaa in a while so this is a good sign.

I can't believe we had such a bad experience with the switch! The vet and the store owner agreed that a full on switch would be better since the Eukanuba and Evo were so drastically different even though I thought differently. But I guess now they both know that was a bad idea
If Moose is still having any diarheaa or upset tummy later tonight or in the morning he will go straight in to the vet! But he seems to be doing much better this afternoon! Thanks again for everyone's help, it's so great to have a place to go to and ask questions without being judged

I'll update everyone again in the morning, thanks guys!

Moose and his Mama