4th gear could very well be a syncro problem, does it grind a little even with the clutch all the way in? There is a little plastic cup shaped thing that the ball on the end of the shifter fits into, in the shift rail, if yours is old and worn out it could cause quite a bit of play. An aftermarket shifter would also make a night and day difference in the feel of everything.
Check the shifter bolts, unlikely but they could be loose. Check that little bushing in there too while your at it. As far as loose handles, I had to put an allen wrench in my shift boot so if it works loose I can tighten it on the go because when it's loose you can forget banging gears. And if it got real bad it was hard to drive period.