How can I export/import accurately my animation keys/tangents from Max to Unity?

I'm working on a project that uses animation characters with facial rigging, max cameras and many other things. The problem is that when I export characters, simple objects or cameras into a fbx format and then I import them on Unity (at least using "legacy" at the rig of the import settings) several unexpected things happen:

1.-My five keys of the animated fbx object turn into a file which has many more keys. (see the attached images below)

2.-When an object is going to make a strong displacement between two consecutive keys, (despite I set the animation tangents on max to stepped), Unity imports it ignoring my tangents adding extra movements before and after these keys. Unity even seems to create new keys between my two consecutive keys.

Is there any solution, please?