My first webtoon episode was around 50-60 panels and I had a really hard time fitting it to the 20MB limit on webtoon.
I could only have the first and last files be png and the other jpeg which lowered the quality (especially the case if you use gradients) so I would advise splitting this episode into 3 since readers get asked if they want to subscribe on the third episode and it'll allow you for more high quality files.
I think having longer first episodes can be good in establishing a lot, but 115 is quite long, even by originals standards. It can be done of course, but it will take longer to get the subscribe prompt on the third episode and some readers just aren't that patient.