Used black eye orb and killed only the thief, not lautrec...orb lost,now what?

If you got the souvenir of repraisal that means you killed Lautrec, and that also means mission accomplished. So, the black orb has no usage anymore, it can only be used to invade Lautrec. You should also have received a Firekeeper soul, 5 humanity and the ring of favor and protection. Check your equipment storage. To see if the items are there. If you by any odd chance don't have the firekeeper soul, then you are screwed....

After killing Lautrec you can get his armor. However, you need to beat Smough and Ornstein to get to them.

The cracked orb is used to invade other players and can be used when you are in human form. Not being able to use estus flasks is normal, you can never use them when in another player's world. Regardless if you were summoned or invading. Heal spells, consuming humanity or cinsuming divine blessing are the forms of healing available.

You get 5 hard humanity, same as the ones you get from rats, find on corpses etc. So it just adds to your number of those.

With regards to S&O, they are tough. I suggest you summon some help. You can summon Solaire, he is available half up the stairs where the Silver Knight with the bow stands. Otherwise, just summon some players if you play online. What level are you? I could possibly help out in a fight if you are on PS3.

Another good tip is to focus 100% on one of them as when you kill the first one the other regain full hit points.

No, Solaire and any other NPC helper will be there to be summoned everytime you are in human form, so even if they get killed when you have summoned them they live on for the next time . Similar to that your own character survives if you get summoned by another player, even if you haven't experienced that as you play offline.

Another tip is that Ornstein is weak to fire, while Smough is weak to lightning. Also make use of the pillars in the room as protection