Yes, was able to use my cell without problems

Sorry I cannot help you, when we visited the Falls recently, the last couple of kms to the Falls was closed for road maintenance and we like others walked in. It did not detract from the scenery but at that point in time no-one was camping near the picnic area. Might add it was the end of winter and not the summer holiday season.

No. There are flush toilets in the parking area.

During the day maybe a bit especially on the weekend. All the sites are close so a noisy camper can cause issues for all.

If I remember correctly, there are cold water taps in the campground. It may be a bit awkward filling your rev, but it can be done

If you just want to see the main falls, it's a 2 minute walk from the parking lot. Some of the other trails around there take around 20-30 minutes.

Campground pretty decent is up on the flats. We had good reception while there last year with Bell.

From Nanaimo go north on highway 19 toward Campbell River. after 30km take exit 51 for highway 4A west, signs for Coombs (turn left onto highway 4A). go 3.3km on highway 4A and then take Errington Road (left turn) to Englishman River Provincial Park (8.7km)

No charge for day use or for the parking.