Not unrealistic.I'd expect it to be a 5 year deal. Just looking at other deals out there that got done recently with their guaranteed money and injury guarantee.
Watson - 230M
Burrow - 219M
Herbert - 193M
Jackson - 185M
Hurts - 179M
Wilson - 165M
Murray - 160M
So I'd expect Tua to be in between Hurts and Murray if he's taking a "team friendly" deal.
I prefer letting him play out the 5th year before doing a new contract, but can certainly see it both ways. There are advantages/disadvantages either way.
As far as slotting him on that list, Watson, Murray, and Wilson are all terrible contracts (from the team's perspective). I throw those out in my reasoning if I'm a GM.