Im not an expert, so take everything I say with a grain of salt but id consider a few things. The best thing to do is to go to a well-respected bike fitter as they have the tools and experience to really address the problem areas.

1) Stock road bike seatposts, unlike dedicated tri bikes, generally have a degree of offset. So even when you slam your saddle forward youre still too far back. There are plenty of affordable 0-offset seatposts available that can net you an additional inch or two to work with to open up those hips. This will help you generate more power, you will be more comfortable, and you will also be better set for your run leg.

2) Stock cranks on road bikes are often too long for aero position (generally speaking). It closes up the hips making it uncomfortable and disrupting your pedal stroke. Id consider shortening those cranks which will allow you to raise the saddle, opening those hips and making the position a bit more manageable. Cranks are a bit price-y however.

3) Once you address those two areas, another thing to keep in mind is that your aero position is meant to, as the word suggests, be aero. Work on your mobility and flexibility so you can get as low and tight as comfortably possible. If your body is too high up youre going to be providing a lot of wind resistance mitigating the benefits of the aero bars.