My question is, based on the results of the calculator am I to assume that I would be okay when it comes to clipping at my listening level threshold and that my speakers/amp were not clipping today at the 90-95 (max reading) of SPL db?
Clipping is very frequency dependent. A lot will depend on your source music. The more lower frequency content the more likely you will get clipping. It is not just an amp problem...speakers compress music because low cost mass produced drivers quickly exceed their linear operating range on most designs - this also leads to a lot of distortion which will make the music sound harsh and perceptively very loud - most noticeable and uncomfortable in the mid range and tweeter. These low cost driver designs are however quite robust and even if they badly compress and distort they will generally survive provided they are given clean power.
There is no reason that good source music should not be enjoyable (i.e. not sound too loud) at 90 db SPL average levels - this is still far far lower than most live concert levels even for classical.
Also, does this mean that I could go as far as a max reading of about 100 before I damage the speakers from clipping?
Trust your ears and not the SPL meter and calculations. If the sound is effortless crystal clear and undistorted then you should be able to play up to about 100 to 105 db SPL at the listening position before it begins to sound uncomfortably loud. The fact it sounds loud at 90 db SPL is indicative of high amounts distortion somewhere ( make sure you have a good source music - well recorded music and not modern compressed pop trash...)
BTW an unamplified piano goes up to 110 db SPL on a crescendo