90% MHR is blooming hard going. Max I have hit is 88% for a 10K. And that is topping out at 214.
Max I can hold, for shortish distances, say a mile, is 193 to 194 on a good day, so yours is not far out in the higher end, based upon what people report here.
56 RHR, age 45. about a stone overweight for a runner.