After you filter your brew after boiling it, you should put it in the fridge overnight. All of those particles should settle to the bottom at which point you should filter it one more time. You say you had 4 capsules of powdered peganum, but how many grams were in the capsules? If you didn't take enough of the rue, this could be the reason your experience lasted shorter than you liked. Not puking should make the experience last a bit longer, but you'll also probably have to contend with nausea for the duration of the experience. If you don't want to puke, that's up to you. Some nexians prefer to hold it down, while others can't wait to get it back up. Personally, I'm the latter and I usually wait around an hour after consuming the mimosa (or DMT portion) and then try to purge. Even with purging, I've had experiences last up to 8 hours, so I wouldn't blame it entirely on the purge. Your 2.5 hour trip I think might be somewhat average for ayahuasca though. Everybody's body processes it differently and there are many factors that can affect it such as digestion, metabolism, diet, etc...
If you find yourself coming down quicker than you'd like, here are some suggestions to remedy the situation. If you have more mimosa left over, you can try drinking another cup. If you no longer have MAO inhibition, you'll need to take more rue. If you have any spice or changa, you can smoke/vape some and that should launch you into the next dimension for an hour or so more, and when that's over, if you've had enough, you can merely stop, or if you've decided you can go for more, just take another rip or two and you'll be back up in the stratosphere for another hour.
"Science without religion is lame. Religion without science is blind" - Albert Einstein
"The Mighty One appears, the horizon shines. Atum appears on the smell of his censing, the Sunshine- god has risen in the sky, the Mansion of the pyramidion is in joy and all its inmates are assembled, a voice calls out within the shrine, shouting reverberates around the Netherworld." - Egyptian Book of the Dead
"Man fears time, but time fears the Pyramids" - 9th century Arab proverb