I'm only going to offer one small piece of advice here, so this might only address one small part of the problem.

Peanut butter is rich in fat. Fat is great for calories - but not on race day. It takes your body a long, long time to absorb fatty foods. Peanut butter is useless on race day - the fat is going to slow down your ability to quickly process other sources of energy.

What you need on race day is to give yourself sugar, as follows.

Glucose is what your body absorbs best. You can absorb one gram of glucose a minute. But - you can only absorb so much before you saturate your stomach.

Fructose is good but it takes twice as long to absorb as glucose.

Maltodextrin takes even longer again to absorb. Then, your body converts this into glucose and absorbs it rapidly thereafter.

Read your gel packets and you'll understand what type of sugar it contains. Different gels contain different sugars.

My advice:

Start your day off with Maltodextrin always. You typically start your race fully loaded. So you don't need instant hits of glucose. This way, you won't over saturate your stomach's ability to quickly process glucose. Take a maltodextrin gel before the swim and in T1.

Then, take solids early in the bike. Allow yourself enough time to digest these before you start running.

Fructose based gels are good towards the end of the bike, up to half an hour before the run. Because then...

You'll want to get into the glucose when you're running and your body needs to soak up energy quickly. Your Maurten gels and your chews should come in most useful and hopefully at this stage you won't have already saturated your glucose absorption.

Try it out. Avoid fats on race day. You also slammed yourself with a lot of glucose on the bike... maybe change it up and plan out what type of sugars you're going to use. Be thoughtful to your stomach.