1. He could easily know about each original Avengers and their power during/after the Chitauri invasion in The Avengers. Know your enemies.

2. With the Avengers at least, they offer some fighting chance, considering Xandar and Asgard were already destroyed.

3. When they met in Ragnarok, Strange helped him without any reserve. No reason for Thor to doubt that, plus Heimdall could have supported it and the reason why he teleported Hulk to Strange when Thanos attacked.

4. Wakanda is only invisible to earth's technology. The Bifrost can deliver the user to almost anywhere.

5. If you paid attention to the dialogues, that was not the first time Wanda sneaked out. So, yes, they were monitoring her.

6. When you say you would welcome people to your home, you don't post your home address on the Internet.

7. Nobody can answer this at this point, only top Marvel executives. Wait for the movies.

8. He has, but as he held on to his principle, the wipeout was done at random, at his behest. He chose not to choose who would die.

9. Comics have various timelines and continuities.

10. He had his army there, or the last location. This is a no brainer.

11. Watch Dr. Strange again on why he can't simply play with time travel. Time manipulation breaks the space-time continuum and makes earth vulnerable to interdimensional beings such as Dormamu. Thanos is not the only threat.