Should "altega" be equivalent here, or does it have a specialized meaning?
"altega" would be fine here. Report it as an alternative answer.
I'd say it works. :)
Mi ne memoris 'plafono'n.uzis 'malplanko 'n. Ne estis korekta!
Why is it Tiu and not Tio? Is it because it is specified which room it is?
"Tio" is a pronoun and can replace but never accompany a noun:
English uses the same word for the two neanings, Esperanto doesn't.