How would you rank these five prohibitions from most severe to least severe: major shirk, minor shirk, major sins, innovations (bidʻah), minor sins?

The most dangerous of forbidden acts is major shirk (polytheism), for it is the only sin that Allah does not forgive unless one repents from it. It nullifies all good deeds and is the greatest of major sins. As for innovations (bid'ah), they are divided into those that entail disbelief and those that do not. Some of them can be major or minor sins depending on how they undermine the necessities of religion. Minor shirk generally falls under major sins, and it may be considered greater than some practical major sins, such as swearing by other than Allah, which can be graver than swearing by Allah falsely. However, not all minor shirk is greater than all major sins, as some major sins may be more dangerous than some types of minor shirk.