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It sounds like it may have too much nitrogen and not enough phosphorous. Plants need a balance between phosphorous and nitrogen to bloom (and fruit) well. I would recommend giving it some bone meal to increase phosphorous. You should also ensure that it receives enough light indoors.

Regarding hollow fruits...this is oftentimes a result of the species (of which there are many). Some species only produce hollow fruits while others produce fruit with edible seeds and some pulp inside. Apparently, you have one of the hollow-producing fruit varieties.

For the flowering, it sounds like it may have too much nitrogen and not enough phosphorous. Plants need a balance between phosphorous and nitrogen to bloom well. I would recommend giving it some bone meal to increase phosphorous.

If you see green, it will come back. This article will help determine if the plant is still alive: https://www.gardeningknowhow.com/plant-problems/environmental/how-to-tell-if-a-plant-is-dead-and-how-to-recover-an-almost-dead-plant.htm

It sounds like it has trouble pollinating. The pollen on this plant is rather heavy and if you do not get many pollinators, you may want to hand pollinate the flowers. This article has direction on how to do this:
http://www.smallcheese.net/2010/04/09/pollinate-passion-fruit/

Most passion flower fruit is edible but there are a few that may be toxic when not fully ripened. Some species taste bland, others quite yucky, and still others could make you sick. If in doubt, don't eat them. In fact, it is probably best only to eat ripe fruit from commercial sources unless you know for certain that it's a suitable variety for eating.

If you do not plan on propagating any additional plants, you can simply cut them off and dispose of them. Otherwise, you can remove the seeds and germinate them for planting.