re: Too little rear grip
I think, there is good advice about toe and camber, above. All of these depends on tires and driver and regulations... Always think that toe, camber and tire pressure work together. Make rear camber same, L and R.
Tire temps should be within 5C or 10F across. 10C or 22F delta is a little
too much.... Where are you seeing 10C delta. rear outer? (is my guess)
The Dunlops are not very popular here (hard to get). So I know least about them. Try bringing rear tire pressure down, if it is safe to 1.65 bar hot, as well. Alternatively, increase front hot pressure to 1.9. (safer, but less traction).
Somebody asked for tire temperature profile out/mid/inside. This would be useful to see not just for the delta but for the difference front to back. Hence, same slick manufacturer on all 4 wheels is more useful for this type of analysis.
You can try adjusting the shocks for more traction in the rear on corner exit.
More general thoughts below....
Wider tire takes less camber, but depends on the manufacturer, as well. I used to run 1.5 rear on 345's. Running a lot of camber on wide tire does not look right. It looks like the outside is off the ground. However, only temperature profile can tell.
A lot of my friends on faster tracks, after racing for many years, are adopting a 0 toe all around. Front toe out helps turn in. However, the srub on the tires creates an interesting temperature profile and behavior. Does a Lotus really need more turn-in? Rear toe-in is for high-speed stability as rear tires are forced to toe-out at speed. If the suspension is all solid, is this necessary in a modern race car? In cornering rear toe-in creates less traction.... again: only temperature profile can tell.
Anton