Hi HazelNuts39,
Why would a slow roll to the right or 8° of bank put so much stress on him?
He had probably never handled the aircraft at FL 350 in Alt Law before. In Normal Law, a small ss deflection left would have commanded sufficient aileron to roll it towards wings level, then if he let go of the ss the roll rate would have been zero.
If you examine his ss deflections in Machinbird's post, he was struggling to find the roll rate neutral balance point of aileron deflection. When he relaxed on the ss, the aircraft continued to roll. Simply holding wings level was taking more of his concentration.