Okay, I mapped out the route as best I could on Delorme Topo USA (a couple turns I wasn't positive about, but it shouldn't make any meaningful difference.
Also, this is based on the outbound route - there is at least one (minor) difference in the return route, but it sholudn't matter either.
So, Delorme shows 2329.7 climbing feet and the climbs cover 21.66 miles outbound. Of course, a lot of them would be very minor changes, but I can't work out all those specifics.
Then I reversed things for the return trip and that shows 2326.7 climbing feet over 21.66 miles.
Put them together and you have 4656.4 feet climbing over 43.96 miles.
But putting a human view on it, we have the following climbs that are particularly noteworthy:
Diamond Head, Hawaii Kai Drive hill (call "Heartbreak hill"), the hill up to Makapuu Overlook. Then you have them again in reverse, though I think that on average, the return is a little easier (at least if I wasn't so tired).
There are other much smaller hills that certainly tire me out, but I can't begin to number them or describe them in any detail - I just know I slow down a lot and lose energy.
And I'm still very tired!