One issue you will encounter is differentiating between a web host reselling web hosting from another web host or a top level web host using an underlying infrastructure provider such as AWS to power their servers.
Is there a limit to the reseller level, not strictly speaking but there is a diminishing returns aspect whereby each reseller is adding their own margin on and after a few levels it is no longer of any value to go any further down the chain as the wholesale price becomes too high to make any money based off what the end retail price will be and to still allow a profit to be made.
There are also specific niche style hosts that specialise in one type of hosting which them use a compatible higher level host which in turn uses a wholesale infrastructure provider. As an example I know of a web hosting company that exclusively used Heroku to power their websites as they liked the automatic deployment and pipelining capabilities so all the sites they hosted for their customers where hosted on Heroku, which in turn uses AWS to host all of their servers. Heroku and AWS are not in the same industry strictly speaking as one is a platform as a service provider and the other is an infrastructure as a service provider.
One option is to perform a trace route query on the hosts domain, which 95% of the time will be on the same servers or at least in the same environment as their customers sites, and by performing the traceroute you should be able to identify the top most level of hosting. It won't show you how many levels of resellers there are but it will show you the highest level depending on how the PTR records for the IP address in question have been configured.