Actually, you have a fairly complex question/requirement.
So, I assume you have done a forum search for keywords like image resize. If not, you might take a look.
Thanks for posting your workflow steps. That is always very helpful.
However, if you already have a macro, even if it is partially complete, it would be best for you to post the macro, and ask specific questions where the macro is not working as you would like.
From my quick look as the Search results for "image resize", it appears there are several topics/macros that are similar to yours. See if you can use or adapt the Actions in those macros. If you have questions about any of them, then it is probably best to post in the thread where the macro is discussed.
No need to be embarrassed. Any macro that gets the job done is fine. It will save us and you time if you will post your macro, and ask specific questions about it. That way we will know where to help you.
See