Well it might be that you have very little lift or you dont have enough control surfaces to actually get yourself pointing up, because you are at 100 m/s most aircraft go up at 40-80 m/s even a super heavy bomber I made took off at 50 m/s When an airplane goes to the side is pretty much because they are going to fast and should pull up earlier. You should first try putting more wings on it :/ See if that works (Note: I am not an experienced FAR user) For spaceplanes if you are just starting you shouldnt use FAR, First get used to ksp default aerodynamics and THEN try FAR