the clutch may be engaging right at the top, but the key thing is whether its slipping or not, and if it is properly disengaging... If it is not properly disengaging your gears will crunch

A simple test to check slipping is to stop your car on level ground, pull up your handbrake, engage 5th gear and quickly disengage then engage your clutch, if the car doesnt stall straight away you are slipping

With regards to your timing belt, if your log books dont state that its been changed to spec, then have it changed

OEM is good, but it depends what you are using the car for, it might be a good time to put a heavier clutch if it suits your needs, but still to OEM for the belt