So first, with the default Paypal ID (i know we marked it as optional) since it can be optionally set within your account settings or within your funnel settings.... I believe we will make it required during the setup process to avoid all problems
Second, I don't really think with funnelish, you need to remove any products or code from your funnel , we have some immergency setup in case if something goes wrong or you need to urgently go back to CF default setup, just TURN OFF the app(s) that's all you need to do:
Once turned off/on all your changes will get applied instantly Live.
Now with the OTO problem, hmm... Have you added your OTO step to our app?
When Paypal doesn't know what step it should go to next, it will just stay there.
I checked your setup and I believe that's the case our platform doesn't know which step to take your customers next, thus it stops at the Paypal's default thank you page
Generally, following the guidance provided on the button you can really go through that
Hope that helps!
PS. Please make sure to post any funnelish questions on either our forum or on our Facebook Group (Clickfunnels Practical - Funnelish)... We can't provide support through CF's main support website