Don't recall it mentioning that you cleaned out the dust that can have a dramatically adverse affect on heat transfer/dissipation from the heatsink. I always try the simplest, least espensive and least invasive solution before buying something else or tearing apart the PC...including the HS FAN
Re higher CFM....there are FANs and then there are FANs....different size fans (60MM, 70MM, 80MM, 90MM and 120MM), different thickness fans 10MM, 25MM, etc.,), different RPMs, and so on. There are fans that run at varying speeds to move much much more air (and usually more noise) that might be used and there are TEMP cntrolled fans that run faster or slower depending on the system TEMP. There are lots of places that sell aftermarket FANS for heatsinks and complete HS FANS ...FROZENCPU.COM comes to mind.
Re heat spreaders...you don't have to go back too far in the AMD or the Intel line to find CPUs that didn't have heat spreaders. My daughter's PC had an AMD Athlon 2200+ and there was no heat speader...nothing like what's being used on CPUs today. The CPU surface area was not much larger than a dime.
Again...these are merely suggestions, alternatives, ideas....you have to pick the one(s)that make sense and work for you. If you already removed dust from the HS, the next alternative (for me) might be to look at better, more robust FAN (for the HS) with variable RPM. If that's not feasible....I'd remove the HS FAN, remove the thermal pad or paste, reapply a good thermal paste like Arctic Silver and see what that does. If no significant improvement...look at higher efficiency HS FANs.
Keep us posted.