I have flown the same heli for a year now. There are times I enjoy the flight more especially in some 5-8 mph wind than my 450 Pro. Seems the flybar handles wind better than the pro V2/3GX.
Regarding the flybar cage. Parts do wear and become loose within the cage. Especially the seesaw assembly. Particularly the screw that fixes the seesaw holder (Align Part: H45140T). I would keep an eye on this part since it will effect blade tracking. Otherwise, the cage fixed points should be tight and without play. Play in any fixed portion of the cage will cause vibration or throw blade tracking off making it impossible to get good blade tracking.
Regarding servo 90. The servo arm should be parallel (90 degrees) in relation to the main shaft.
The heli should come off the ground at about 5 degrees positive pitch.
When the blades are at about 5 degrees and you have enough head speed she should get light on the skids. If your cage is loose this may be effecting the blade pitch and could cause her to hit the dirt before lift off depending on the pitch of either blade.
Check the blade pitch at mid stick (with motor disengaged of course).