Huzzah! You, sir, are a champion. Thanks for confirming that.

Ah, seems I was the one mistaken about the Bone:

http://darksouls2.wiki.fextralife.com/Bone+of+Order

Felt like doing some research for you. Try using that and see if anything happens. It seems disconnecting does impose a sin penalty on you. Try not to do it in future =]

The Bone of Order is used to reverse the effect of burning effigies in a bonfire. Which area are you in when you get invaded? Is it everywhere or is it just limited to one location? Some areas are PvP hotspots and you'll get invaded a fair few times while you're in them by Brotherhood of Blood members. If this is the case then burning an effigy at a bonfire will greatly reduce the invasion chance. Being Hollow reduces it more (if you need help with a boss then restore your humanity next to the fog gate to the boss).

If Cromwell is charging you to absolve you then you accumulated sin somewhere. Did you kill any friendly NPC's?

You can actually have sin that doesn't show on your player profile, and I'm pretty sure it takes multiple sins to earn the first status, but you can get invaded by Sentinels with even +1 sin, as that targets you as a viable candidate for the Cracked Blue Eye Orb. It's possible that the red phantoms you're seeing are Sentinels, but I wouldn't put it past being Brotherhood members either.

I haven't heard anything about disconnecting causing sin but if you feel conscious about it then pay the 200k souls. You'll be sitting on a cache of them in NG+ anyway. I'm SL152 and have 300k currently.

Nope, he just dropped his hood when I killed him. I was human at the time. If he does drop the spells then it's a rare drop rate and you only get one chance. You can only do the assassination missions (and receive the spells as a reward) if he's still imprisoned. So you'll have to NG+ it. I made the same mistake and facepalmed so hard.

You don goofed. I hope you killed them by accident :P

Otherwise all I can say is you'll have to wait until NG+ to talk to them again.

There's 3 giants in the forest that it can be used on. Which two have you done?

Start from The Mines bonfire in Harvest Valley, turn right out of the cave and right again (watch out for the holes). Go across the bridge with the ugly dude and his hammer and turn left. Go all the way to the end of the ridge, into another cave (beware of a sickle-wielding buttface in here) and follow that cave into an opening. There will be a broken statue to your right which you can pray to in order to join the Heirs. You also offer Sunlight Medals to this statue to rank up.

You mean the one with the fur around the shoulders? That's the Faraam set and you can find it in Drangleic Castle very near to the King's Gate bonfire. Outside that bonfire room there is a hall with 6 doors, all sentried by stone knights (5 of the rooms contain Ruin Sentinels so don't run into the room). The far left-hand side door will contain a Sentinel and a hole in the floor - drop through that and there will be a chest with the Faraam set inside, along with Darkdiver Grandehl and another bonfire.

Pretty much that. He's a little whappy in the head so I'm not sure he realizes he's taking you for granted. Benhart and Lucatiel will give you their full sets, and Vengarl gives you his helm just for talking to him. Don't worry yourself over it, you got the achievement. If you still feel spiteful towards McDuff then go back before you start NG+ and smack him with a Washing Pole.

I'll second the Alva armour, it provides amazing physical defence even when it's not upgraded. Another set I like is the Black Robe, which gives good physical defence and even better elemental resistances (switch between Alva and Black depending on the enemy). You can get the Alva set from Maughlin after spending 16,000 souls in his shop (although the breastplate costs 8,000 alone), and the Black set is given to you by Straid for spending a similar amount of souls.

The Tights of Judgement you get from behind a Pharros lock in the Dragon Shrine is also one of my preferred leggings.

@indzman Lure those guys out and fight them one-on-one. Depending on your build their attacks are simple enough to dodge once you learn their animations. They normally attack in strings of three, in which you should be able to land a hit or two, or more if you manage to stagger them (they're easily staggered). Taking them on as a group is a terrible idea. I think even awesome players would struggle with that so you're not alone.