Answer: Yes, when you first start playing all of those things are normal.
Trying to summon a specific person as opposed to a random can be difficult at times. There are a few tricks though
A) Do not place your soul sign in a high traffic area.
-For instance when I play with a bud in the parish, we usually put our soul signs down by the body where the firekeepers soul is. Try to put it in a location that is accessible, but out of the way enough to avoid other people from touching your, or your buddies soul sign. Other people trying to pick up your friends soul sign can contribute to fails.
B) Only spam your sign to try and get it to show up in your friends world. After that, place it and let it sit. From my experience, spamming your sign can also lead to fails. The summoning fail rate (from my experience) goes down drastically when the soul sign is left to sit between 30 and 60 seconds.
C) If you are not talking on the phone or through skype, then use a chat room. Also use abbreviations. Like ssd (soul sign down), rss (relayed soul sign)...obviously you'll develop a shorthand code that will allow you to communicate in an efficient manner without having to spend time sending long drawn out messages.
***After awhile you'll see your summoning time go from 20-30 minutes to 3-4 minutes (most of the time). I practice these techniques everytime when playing with a friend. However, there are still days where it just takes awhile to summon a specific person. But I haven't had to wait more than 5-10 minutes to summon someone specific in a loooooong time.
2) Op'd invaders.
Ya. Not a whole lot you can do about it. When you are playing with someone who is also new to the game, and you both have level appropriate gear on...there's not much you can do. However, you can summon a phantom that looks strange. What do I mean by that? Well, if you know there's a d-bag invading your area that is op'd and unbeatable...summon a different phantom while you wait for your bud. If you see a phantom that has some gear on you are not familiar with, they might be an anti-griefer build.
Some vets create low level phantom builds for this very reason. They will have ZERO problems waiting for you to summon your buddy and will take great joy in fighting off invaders while you wait. Don't take advantage of them. Don't expect them to wait a half hour or something. Keep them healed, drop them a humanity or something, and they will defend you with their life.
3) Most importantly...DONT GIVE UP MAN!
Before too long when your cherry is popped and you become numb to the griefer experience, you'll find yourself with an anti-griefer build of your own, only playing with it at sl 20 to see how many invaders you can kill and to see how high you can get your multiplayer bictories up to.
GOOD LUCK....and welcome to Dark Souls.