If your rocket is able to maintain that 280° angle (relative to prograde) throughout the re-entry (either manually or using my Smart SAS mod), then you can use the "current angle" option for the "simulation type" setting to predict the trajectory based on that angle, instead of strictly prograde or retrograde. The next best option - in the case of a changing angle relative to prograde - would be the "min-max range" option, which predicts the trajectories for the angles of minimum and maximum drag forces (approximately). Being able to predict a changing angle would be both impossible (as I can't predict future player inputs ofc), and computationally expensive (since afaik calculating the surface data required for the drag force is quite expensive). The final option would be using the gliding heatshields mod to make corrections to your trajectory throughout the re-entry (gliding heatshields' forces are also included in Aero Trajectory's simulation when the mod it's installed).
Thank you for the response and have a good day!
(Unrelated, but since you mentioned you made the Smart SAS mod, I decided to check, and it turns out I seem to have all of your mods except for forceful fuel tanks installed! Thank you for making awesome mods for us to use