Yes, in order to give a user access to multiple locks, you'll have to connect to each lock to add the guest, and repeat for each lock. We know this isn't ideal and we are working on a web portal that would simplify the process. Stay tuned!
Unfortunately, using the API will not increase the number of users supported by each Sesame, as the limitation is based on Sesame's internal storage - Sesame itself can only store up to 100 access keys, and that's where the limitation comes in. Hope this helps, and feel free to let us know if you have any further questions! - CANDY HOUSE