I've a lot of Pothos up in trees, up to 20 metres high. And you're right, the leaves do get very large. The ones in the ordinary trees don't get much direct light, but some up in Palms do get direct light most of the day. There isn't much difference as a result though. The Philo looks like lacerum, but a bit hard to tell. My P. lacerum is also getting right up in the trees, although not as high as the Pothos. I still suspect your biggest problem might be the excess water. However, neither of these two species are in water in my place so I don't actually know how they'd respond to it.
