Isolated Flyback PWM controller with on-chip FET

I wouldn't suggest a on-chip FET for 35W in that input range.. 
The input current i typical too high.

35W/85V = 0.4Arms.. Your peak current in inductor and FET is around 4 times higher than this.. = 1.6A..

This could be your answer: http://www.ti.com/lit/ds/symlink/lm5021.pdf (LM5021). When using a Flyback, use the -2 version since the IC's duty cycle is below 50%.