A lot of the extra experience points came from doing things in a very specific order rather than trying to escape as soon as possible.
People keep claiming this but I do not believe it is true.
Do you have any numbers to support this except for Elodie (XP200 ish) and Dallis Pets (XP2880 each)?
Sure if you do everything you will leave at level 5 (or 6 if you kill Dallis pets) but the order does not matter. I have played this part probably 100 times and the order makes no difference. You always get the same XP.
The only serious difference is if you engage Dallis (and therefore get XP from her pets) before you leave or you don't. If you don't you miss that chance.
You can choose whether to get XP from things (like Stingtail/Griff) but when you do it is immaterial - you can pop back at level 8 if you want and you will get the exact same (couple of thousand) XP. I know as I've done it.