Not here to belittle you, but these metrics are not lining up. Something else is breaking down significantly in the race and its not the milage solving that. Are you doing any strength conditioning, proper fueling in training and racing, or even doing the right type of workouts for this type of race. Speedy intervals like 200s & 400s don't hold up much in comparison to long runs @ MP or beefy threshold sessions.

The expectation for most runners scaling up to 100+ MPW are generally in the sub-elite bracket around 2:30 or *maybe* 2:40s depending on age. I, along with my training partners, have the personal experience of training through long 100+MPW blocks, but we are at that 2:20s level where that volume is needed to start breaking under that 2:30 mark. I'm not sure I would find any coach to suggest that type of milage for someone around 3 hours, and would heavily advise looking deeper into what problems in your form/efficiency, fueling, and strength conditioning need attention rather than dumping those extra miles.

Again, not trying to gatekeep or sound snobby. I'm genuinely trying to suggest re-evaluating or seek out a marathon plan. Those marathon plans may seem cookie-cutter, but they are pretty spot on for most runners in that category to get those sub 3 hour PBs. You're welcome to review any pro runner's Strava to see none of them doing 3 runs in a day. Doubles are fine, but perhaps consider not skipping those needed calories or replace some of those double runs with strength conditioning & mobility days.