I've been reading deja articles for hours on separate days - but I
would like some quick advice if possible. I'll try to keep the story
short.

Moved into a condo; very old Lennox upflow heating/2-ton air
conditioning unit. 900 sq ft open space (no bedrooms/doors)

The air that comes out of the registers is _somewhat_ cold - but not
cold as I like it to be. As a result, I can only maintain the indoors
temperature at about 78, no lower. I would like to get down to 70 if
possible (outside temp 80-95).

It appears that the previous owner did not have an air filter where the
air got sucked in by the fan... so I put in a new filter. Due to the
way the unit is positioned (basically inside a closet) - I'm not sure
if having a filter is causing a problem by possibly restricting intake
of air.

There is no icing on the pipes at the outside condenser unit as I can
see. The alum fins on the condenser unit looks ok, free of debris. I
had a guy come out and fill it with a pound of R22, he said it was low.
I did notice some improvement, I can go down to about 76 now, but
still I would like to go down further to 70. Am I asking the unit too
much?

What else can I check to narrow down the issue. From reading some
posts, how do I check evap coils (this coil is different than the
condenser right?) & condensor/coil water drain (not sure where this is
located)?

I realize that the AC guy is supposed to be doing this stuff for me,
but to make a long story short I do not get to choose who comes by to
diagnose the unit. In the event I do have to shell out money, I would
like to be informed.

Thanks for any suggestions.