Hi There,
Changing stack shouldn’t break your design. It should pickup the design for Ethos. Unless you have custom CSS that is conflicting with the new stack default design the issue might happen. I have checked your site and see that you have caching and optimization. After every update note to clear cache before checking again.
If the issue persists after clearing cache, please give us more details on which part is broken. It would really help if we can see the issue directly. If it’s totally broken, please setup a staging site and do the switching of stacks there so we can check while your live site is still working. Note to disable caching while we’re checking.
For future reference, please note not to bump your thread. We are answering from oldest to newest and bumping the thread pushed it back on the queue.