Honestly, it looks like you didn't even go to these hotels but downloaded images from Trip Advisor and extrapolated information based on their own summary and customer reviews.
Seoul rooms are going to be small.Try around Chungno Sam gak and Dongdae Mun, they have better priced rooms. Wangshimni station has a lot of clean love hotels that aren't on the English booking sites. If youcan find some one that reads Korean, or you are willing to spend sometimes with Google translate, go to naver.com it's Korea's equivalent to Google.
Of all the hotels mentioned, only one has an indoor pool. Is that mostly going to be in more expensive hotels or is that not a popular thing in S Korea?
Pools are rare at hotels in Korea, some hotels have bathhouses. I think Lotte hotel has one.Larger bathhouses with have lap pools are common all over the country. If you are just wanting to relax bathhouses are wonderful.
most koreans do speak english (younger generation) because they study english in school so know bits of english. i would think that hotel staff have more advanced english skills but if you do get lost in public you can easily ask one of the young adults or teens for help just make sure not to make your speech difficult
