Yes, you can fill with potable water, then dump when you leave. It is just like a very large, very crowded, dry campground that you will find in most national forests. But it is much more expensive than a USFS campsite because it is in a national park and run by a concessionaire!...

Yes, the dump has potable water, as does the nearby visitor center. The adjacent marina also sells bottled water....

You will likely need to purchase a second site. All of the sites allow 2 drivable vehicles and the reservable sites with partial hookups are large enough for an RV and tent. There is no dump station at this campground. Some of the FC-FS dry campsites may be large enough for anRV, tent, and 2 vehicles, but many are not very wide....

There is only one FHU site at Mound Valley and that is the host site. And only half the electric sites have water hookups--ours didn't. So, if you fill your fresh tank when you arrive and can wait to dump until you leave, any electric site should work, if it is long enough. This is an older COE cg., so it has many more sites 40' than 40'....