Move 6:
This move is usually bad, because it is too measly. Black still has S16 later to aim at the 3-3 point, and if white answers at R17 then P17 is in very much the wrong place - it would be better at O17.
White does not lose many points, and is hard to say is particularly bad, but this reason is enough to make the move important for a strong sdk or dan level player.
If white does not want black to take the 3-3 point, then he should not play the 4-4 point in the first place. The 4-4 point does not take the corner very well at all, so he needs to add this non-ideal move to finish it. The correct way to play, after O17, is to be happy if black takes eh corner because white will become very strong on the outside.
White R16, Q17 or R17 are all fine, and are better ways to take the corner if that is what white wants. Even with these (except maybe R17), one must be flexible, and let the opponent into the corner if that's what they really want (in exchange for a loss on the outside).
Move 7:
This move is fine. I wouldn't say it is the 'normal way to play' for strong internet players. This particular shape is quite popular at the moment, along with Q10. The reasons for this are relatively advanced opening ideas to do with black's options if white plays P4. It is great to see something on the internet and try to incorporate the idea into your own play (it is a strong idea!), but don't fall into the trap of thinking it is the 'right way' to be strong or anything.
Move 8:
This move is probably quite bad, though not so bad as to immediately give white a terrible disadvantage. The reason is, after black plays P4, white's stone isn't doing anything. It does not have a base, as black can play S6 later to undercut it. It has given black the P4 move which he really wanted to play (to make the corner shape perfect), and it does not attack the Q11 stones - which are actually quite well placed to hurt Q6.
That said, white has R9 and R5 to make some shape, and the R14 stones are not completely safe. White may be able to make it work, but I think this would be becasue of bad black play more than white having a particular strong way to use Q6.
A more normal idea here is to just play O3 (or perhaps O4, though much less common), and let black make some use of the side in exchange for making white strong on the bottom. White can still invade on the right later, but this way would not be making black strong on the bottom. P4 and P3 are also perfectly fine, but aren't played because black has some specific moves that cause white some trouble. This is a bit of a grey area, we often say that P4 and P3 are 'bad', but when it comes down to it they have been played by professionals at various points, so I think we sometimes give too much weight to this idea

.
Overall, Q6 is a bad move played for good reasons. White is thinking about what he wants. Playing more games, and trying the alternative, should give a good idea of why white is misguided.
Move 11: You have illustrated some good options, but are rather pessimistic about things. You say that 'However my feeling is that no matter what I do, white is on the offensive.', but...the position is fairly symmetrical, with black to play. It cannot possibly be white attacking, because it's your turn to add the vital move! I think R10 is quite good, as you have suggested, because it helps to settle your stones whilst leaving white a problem - it would be annoying to let white get S11. Playing S11 yourself seems a bit slow. Again, though, the most important thing is to play games and try all these things as and when the opportunity arises. And have more confidence in your stones equality with those of white's - he isn't on the offensive just because he played a move you didn't expect!