Are there any limits per day/month in terms of scheduled posts?

No. The only limitation is the number of posts saved in the queue. If you will empty your queue quickly (for example schedule all 100 posts from Basic account limit in just one hour), you can easily schedule another 100 posts for the next hour etc.

Basically, you can post multiple times more posts daily than the pending post limit of the account – you just need to keep adding them to the queue.