I'm looking at running a network of free sites using JMS2Win but I need to confirm that I can:
1. Deploy ads via the com_banner component on all the sites without the site owners being able to change my banner content nor the banner position on their site.

2. Also unlock the banner component permission thereby giving the slave site owner access to be able to change and upload his own banner content.

1.a) com_banner is not an extension that can have its content shared.
See the list of extension that are currently defined for the sharing
www.jms2win.com/en/list-of-extensions?vi...id=269&Itemid=53

Instead of com_banner, you can use the "Ads Manager" that can have its content shared.

1.b) Concerning the access and the modification of the position, this depends on your joomla version.
If you are using Joomla 2.5 or higher, you can use the ACL to restrict the access to the specific component and also restrict the access to ALL the modules.
In Joomla, it is not possible to manage the ACL per modules but this give access (or not) the the module maanager. So if you forbid the access to the module manager, the user will not be able to change the position.

2) See the standard Joomla ACL to see if you can restrict like that.
I don't think so.
When you give the access, this is for a specific joomla profile and not for a specific user.

3) If you want to avoid banners modified, in general, it is better to hardcode that in the templates - So that, the postion and the content can not be touched via the joomla back-end. (Except via the template manager for which you can forbid the access).

Is "Ads Manager" able to share its content on its own or is something from JMS2WIN needed to share ads between sites?

Yes the Ads Manager is present in the list of extension that can have its content shared.
See list of extensions
www.jms2win.com/en/list-of-extensions?vi...id=269&Itemid=53