Check out that link that Monega posted. At lvl 70 you'll be fine, I'm the same level and I can get a few hundred kills. You don't have to use prayer potions though - you can use bones to peaches.
Go in FRONT of the telescope if you can't get under it. I've had the same problem; the alternative I've suggested will probably work. You need to go through the tunnels to get to it.
No. A skiller can be someone who is combat level 100, but likes pursuing skills of extracting raw materials and then making a product out of it using another/same skill.