what happens after b4? Won't e4 pawn be lost?

so sure maybe e4 is lost. But does that mean black has advantage? his position is terrible and development is lagging far too much. You are focusing way too much on material. With whites huge advantage in mobility and all the open lines into blacks position i fully expect that white would win.
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bc4 e6 7.Bb3 b5 8.0-0 b4