Guys what is the damn max supply of this coin?
30+ billion is already in circulation.. is there an end to this?

No there is no limit of coins in circulation:
https://siastats.info/supply_inflation.html The number of mined coins decreases with every block, but the minimal will always be 30KS/block. However, this number will be less and less representative of the total coins in circulation: check the Inflation chart (second chart) on the link I provided.
Also take in mind in the future Proof of Burn mechanics will be used for hosts, so some coins will be burnt. With the proper adoption of storage, Sia can even become deflationary. Also, more adoption of the storage means more coins locked in contracts and collateral, so less circulating coins.
Sia needs to adopt a basic "free" model to bootstrap the network, gain credibility and get some measurable market share...
With charges for enterprise or non-standard services or heavy usage... or someone else will do it for p2p storage.
There is nothing radical about giving away limited free web services to gain market share.
The average pricing a renter pays right now is $1/TB/month: that is close to nothing (compare it to the $23 of Amazon S3). Each host is receiving less than $0.50/TB/month. We can not ask hosts more efforts providing free storage. However storage providing companies that use Sia as a backend can offer free storage to their buyers and pay that part to the hosts. But this is something it should not be implemented at the network level
Is there any information published on how much space is actually being used on the Sia network? I'm not asking how much total space is available to use but rather how such space is being occupied right now?
90TB currently:
https://siastats.info/hosts_network.html