You shouldn't be doing this yourself. I would have called insurance back immediately after the first job and told them it was unsatisfactory and led to further damage (provide photos). It's their job, they need to make it right. You could also suggest that the dealer was the only place that could make it right (and wouldn't have created the problem in the first place).
It cost State about 3 x dealer price to replace a windscreen once for me because they refused me dealer service, the new screen leaked, I had to take it back to the original place, they couldn't fix it and eventually it went to Mitsubishi (it wasn't a BMW of course) who did it properly.