Also, according to that commercial.... have I been pronouncing Tamagotchi wrong for like 20+ years??? O_O
No, you've been pronouncing it correctly.
The people in the commercial are pronouncing it wrong, which is embarrassing for such a high-profile "revival".
This incorrect pronunciation originated from incorrect information provided to those behind
Tamagotchi Video Adventures, and that same information was also provided to some members of the press at around the same time (or perhaps those behind Tamagotchi Video Adventures did their research and thought that the press were correct - it could go either way, but at this point I have to assume that some well-meaning individual has been referring to old reference materials for the new ad, and that the same info was given to the production-company back in the 1990s). It's also where the falsehood that Tamagotchi translates as "cute little egg" comes from.
To be absolutely clear: Tamagotchi is a portmanteau of "tamago" (egg), and "uotchi" (katakana spelling of the loanword "watch"; The "i" is silent in Japan, but is pronounced in Western promotions because it sounds exotic and catchy), and the correct (Western) pronunciation is "Tamm-a-gotchee" (or just "Tamm-a-gotch", in Japan). It is not, as the false information claims, a portmanteau of "tamago" and "chibi", and it is not pronounced "Tamm-a-go-chee" as per that and the Tamagotchi On commercial.
For what it's worth, past commercials, dating all the way back to the late 1990s, got the pronunciation right.