What kind of substrate do you use?
I use aspen.
A friend of mine uses Desert Snow for his KSBs (& other Sand Boas).... which I have used, before, and would not be opposed to using again.
....all the ones i've ever held have bit me.
Only one, of mine, has ever bitten (& may again) but that has only been on an occasion, or two, where she thought she was getting "finger food".

Other than that, she is a real sweetheart during handling, etc.
My other KSBs have never bitten, not even once (nor under any circumstances), ... and are, genuinely, as sweet as can be.
One of my friends breeds KSBs and his are not prone to biting either... although I can't say that about a couple of other Sand Boas (non-Kenyans) of his.
However, I have heard of a "few" biters (KSBs) that others have owned &/or do own... or, as with you, have held/encountered.
I think they're cute but don't like that you cant see them when they're in their cage cause they're under sand!
I see mine "out & about", here or there, if not digesting a meal (more so the females than male). Granted, they do like to be burrowed, under their substrate, but ... they will come out, to roam around a bit, too.
'Course, then there are always the times that the KSB can be taken out of its viv for "quality time".
What are the heat, humidity, etc. requirements on these guys?
Cool end upper 70's to 80 degrees. Middle to warm end in the low 80's to 85 degrees - and a basking spot of around 90 degrees & no more than 95 degrees. It does seem, however, that lacking a high temp (90 to 95 degree) basking spot is not a detriment to KSBs (though it is a must for gravid females)... others seem to have had this experience and mine do fine, and have done fine, without a 90-95 degree basking spot.
Night time cool side temps can drop 5 degrees +/-.
Humidity should be low ... but do provide a small bowl, of drinking water, that the KSB can have available on a daily basis.
Other than low humidity, a small bowl of water, correct temps, and substrate deep enough to burrow under ... they do not require anything else other than feeding and the maintenance of a clean environment.
Some people will provide hides but they do not seem to be an absolute necessity since KSBs would prefer to burrow rather than lay in a hide.
However, some KSBs do seem to like having something on top of the substrate to burrow/lay under.