You are welcome.
I strongly suggest you to follow the tutorial along:
https://github.com/pettarin/icarus/blob/master/tutorial
Executing aeneas directly "inside" Sigil: you are right, it would be nice. However, it poses two main problems:
1. the user must have the aeneas toolchain installed (the Python aeneas package, ffmpeg and espeak) --- hence the generation of an aeneas ZIP job, that can be uploaded to aenesweb.org by those users unable to install aeneas on their machines;
2. aligning an (audio, text) pair might take from a few seconds to several minutes, depending on the length of the audio and the number of fragments. The user will have Sigil "blocked" for that time, as I think there is no way, in the current Sigil plugin architecture, to put the aeneas process in background.
Plus, Sigil is incorporating EPUB3-related features (the next version, v0.9.3, will have "native" support for e.g. editing SMIL files), so I doubt I will work more on the "computing" side until the Sigil infrastructure will be more defined.