Hey there, Bee,
The answer is 'yes and no,' actually. The wobbling - the loose handle is actually rather typical of Cybex prams and pushchairs, I also don't like it as much. Some looseness is, however, normal, yes, it helps the frame endure the shocks from the road to not break. The bad news is, if it's too much, it is not normal, so it all depends on how much it wobbles and how much it bothers you. I will certainly recommend consulting the place you bought your stroller system at and showing (or making a video) what is happening and how much it causes you trouble. They should be informing you about what can be done.
About the bassinet incline, a bit of incline is just fine and actually good for reflux babies. A 10-degree incline seems a bit too much - if it causes your baby to slide down, I would again go to the seller and complain about a probably faulty piece. The first aid of a kind that you can, however, do, is to put a rolled towel roll under the baby's knees to help him of her stabilize in the position he/she's in and not slide down. It is also an ergonomic position helping with gas ;-)
We would most certainly appreciate a review of your Cybex Melio as it helps other parents make their choice (we tried our best to help you as well). Thank you so much!