He got extremely lucky with Webber being called into the pits to get him out of his way, then when Webber rejoined his accident basically caused the second SC - the lap after Vettel had come in for tyres. That put him a few seconds behind Raikonnen on the freshest (option) tyres of all the runners - he really should have gone on to win it had he not taken so long to get past Button.
He was very lucky that Senna didn't end his race much earlier as well.
I'm not sure what you are suggesting here - the accident wasn't caused by Webber. He was as much a victim in this just as everyone else. I'm also not sure what is wrong about the team bringing Webber in. He's out of contention for the WDC anyway - would we be expecting anything less? Seems a bit odd that Ferrari can practically run a one-man-team the entire season (or most of it), get their 2nd driver to perform extraordinary maneuevers to try to give his team mate an advantage in qualifying, yet god forbid that Red Bull took Webber into the pits giving Vettel a free pass.
I'm not a fan of team-orders either - but it'd be stupid to not have let Vettel past Webber, either by direct team order or any other way. He was the quicker driver (at that stage) and he was clearly on a run. In regards to both the WDC and the WTC, it was beneficial to let him through.
The point on fresh-option tyres isn't a simple one either. Vettels car was set up for overtakes, but the set-up also compromised his "clean-air" pace. This allowed him to get past the midfielders easily by having a higher top-speed, but would always prove to be difficult, if even slight disadvantegous against closer paced machinery like the McLaren or Ferrari. Overtaking Button was tricky because Button also had DRS when running close to Alonso, so Vettels DRS advantage was nullfied. Once Alonso pulled away from Button, Vettel closed the gap, but his compromised set-up ment that he fell behind slightly in the crucial parts leading up to the DRS zone, hence why he changed his approach and how he used his KERS to allow himself to get past Button.
The opportunity to get close to Alonso was there, but given how Button being able to use DRS nullfied his own advantage, made things too difficult.