To put the button (~orderbutton1~) on the order page you would paste the code ~orderbutton1~ where you want the button to appear. I'm not sure what you mean by dynamic. If you mean that you want the payment to go directly to the member then you would need a pro system, with the commission tracking plugin, with direct payment turned on, and then you would link to the join page and payment to the member is made AFTER they create an account (a key difference as direct payment works opposite from a normal system).
Yes, it will suspend them. We caution to be careful if you have more than 1 tier, or an admin payment because the person gets logged out when only 1 of their possible many subscriptions is canceled.
A member cannot belong to more than 1 membership. Instead, you can setup so each membership has different content.
Then make the membership that the member upgrades to include all the content from the member's original membership.
You can do this by setting up content groups and attaching them to content.