Is one allowed to say brachos in the presence of his wife if her hair is uncovered and they are at home and the woman does not cover her hair at home (ie if she does not cover her hair it home, in the home is it considered to be an ervah)
No, even when the husband and wife are at home alone, when her hair is uncovered, although he may look at it, he may not make any brachos or daven when he can see her uncovered hair. In fact this is one of the very reasons (among others) that the Chofetz Chaim advises that women should cover their hair even when inside her home- because her husband or children may not realize that her hair is uncovered and they may make brachos then, which would be an aveiro.
M:B 75-10, Letter from Chofetz Chaim in Chofetz Chaim Al Hatorah pg. 323.