Glad you enjoyed the lesson.
Sure. I can try and help.
You don’t need to necessarily wait till you get up to the 5th fret to play the open third string. You need your two hands to operate independently which is tricky.
Both the slide and your right hand are playing the (2 and) rhythm. You could work on playing each on it’s own and then try and blend them together.
If you get up to the 5th fret a little faster that’s fine too, just make sure your right hand is keeping a solid rhythm.
It’s a little hard to give you advice without hearing you play it but my guess is you could be sliding up too quickly which is throwing off the rhythm of the lick.