Asus Probe is useful software.

As a general rule I tend to prefer the tools that are supplied by the motherboard manufacturer as they understand how the board is laid out and the sensors calibrated.

I have tried several "third party" software offerings and have found the results to be inconsistent. Sometimes they seem to work, sometimes they do not.

Another rough "guideline" is to try to keep the temperature below 50C above that and instability starts to creep in IMO.

Another "target" is that the MoBo shouldn't be much more than 15~20c above room temperature.

You might like to look at one of those flat "exhaust fans". They mount like a PCI card and will get the stale warm air out of the case.

Also, invest a few cents in some cable ties and tidy everything up so that you have a good airflow.

As for the CPU, I never buy those retail kits. I get an OEM processor and a much more competent heatsink/fan combination. Coolermaster are quite good, and I use Arctic Silver or similar silver based thermal compound. NOT the white "gunk" that tends to come with the heatsink.