The spelling of "un stabler" is correct. The word "unstable" has the root word "stable", which is pronounced as /ˈsteɪbəl/. To form its opposite, "unstable", the prefix "un-" is added, which is pronounced as /ʌn/. Therefore, the correct phonetic transcription of "unstable" is /ʌnˈsteɪbəl/. In order to change this to the comparative form, "-er" is added, so "unstabler" is pronounced as /ʌnˈsteɪblər/. However, it's important to note that while this spelling is correct, it's not a very commonly used comparative form of the word "unstable".
There is no dictionary definition available for the term "unstabler."
The word "unstabler" does not seem to have a clear etymology as it is not commonly used or recognized. Additionally, "unstabler" is not listed in most reputable dictionaries. It appears to be a derivative form of the adjective "unstable", which means not firm or steady. "Unstable" is derived from the Old French word "instable", which can be traced back to the Latin word "instabilis", meaning not stable or unsteady.