Yeah something definitely doesn't add up regarding the 7 degree difference with no flow, but it still seems like an undersized loop. You EWT is shooting up almost instantly.
I calculated my loop to contain about 100 gallons of fluid and my flowrate is around 10 gpm. So at a minimum I get 10 minutes of the same EWT before it starts changing. You're seeing a 4 degree increase in 4 minutes. That's not right.