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It should climb up the trellis regardless of light. You may want to try tying it to the trellis initially to encourage it to climb.

Sounds like you may have a problem with mealy bugs. Here is an article that you may find helpful: https://www.gardeningknowhow.com/plant-problems/pests/mealybugs-white-residue-on-plants-leaves.htm

Ivy needs light, but ferns typically do ok in lower light. It may be a watering issue. If they were in indirect light, you may be over watering them. Check the soil before watering. The remaining ivy will regrow leaves and new branches if you clear out the dead material.

I am not sure what kind of worm that is, but if you send a picture, we can try to identify it. To tell the truth, ivy is nearly impossible to kill, so it is unusual that they are able to.

Regardless, I would recommend trying neem oil. It is effective against bugs that suck or chew on plants, which it sounds like they are doing. Here is more information on neem oil: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm

Prune them and they will grow. Leave them alone and they'll grow. Ivy just likes to grow...and grow...and grow. Time is the only key. A living fence of ivy will take years to flesh out unless it's Boston ivy, which will grow sometimes 20 feet in a year. You can interplant Boston ivy with the evergreen varieties. Boston will die back to the branch in the fall and looks dead, but leave it be and it'll come back in the spring.

These articles will help you:
https://www.gardeningknowhow.com/plant-problems/weeds/kill-creeping-charlie.htm
https://www.gardeningknowhow.com/special/organic/homemade-pet-friendly-weed-killer.htm