Mistakes in a Bracha and the placment of Tefillin

I have two main questions. Firstly, during a Beracha, I understand if we error we can repeat the blessing from Vitzivanu in the amount of time it takes to say “Shalom Alacheim Rav”. However, if it is a long blessing, such as before the Shema or Birkat Hamazon, it is hard to return all the way to the beginning and may take a page flip which will cost a person the two seconds. When, if ever, can we just repeat from the word that we messed up on? Or perhaps this is always allowed? Also, if the error is as small as pronouncing a hard Sheva instead of a flowing one, does that necessitate repeating? Second, I have a question about Tefillin. I am very careful about the placement vertically to keep it at or above the hairline, and this is not a problem. However, it seems that my Tefillin constantly moves horizontally. For instance, when I looked in the mirror after the Shema this morning, I could not escape the fact that the box was slightly tilted and had to perfect it and repeat. Perhaps I keep my head fastening too loose, but this is because I wear a large kippah and do not wish to rewash my hands if I were to touch a usually covered uncovered part of my head/body (although I notice almost everyone else does not seem to care). Is this slightly horizontal tilt something I should be worried about? Thank you for your time

ב"ה Shalom I found it difficult to answer your first question, without you pinpointing a specific situation, since there are so many variables. However, in regarding a Sheva Na or Sheva Nach, though to begin with people should pronounce things properly, after the fact, what I have seen from the poskim, it does not necessitate repeating. As far as your Tefillin, According to Piskei Teshuvot, (27:18) once you've properly placed your Tefillin between your eyes, you need not concern yourself by looking in a mirror or by asking a friend to check it. All the best and Shana Tova