Yes.
Yes, you are right.
Literally: "Он съел ужин и пошел спать". (In fact, the verb "поужинать" is preferable in this situation. "Он поужинал и пошел спать".)
But there is no direct mapping between English and Russian Aspects. You should analyze every single situation to choose the correct Aspect:
"Dr Nixon taught at the Oxford University last year." - "Доктор Никсон преподавал в Оксфордском университете в прошлом году." (an iterative/habitual action -> imperfective)
"I met your brother the other day." - "На днях я встретил твоего брата." (a single completed action -> perfective)
"He left 10 minutes ago." - "Он ушел 10 минут назад." (a single completed action -> perfective)
"I read "David Copperfield" yesterday." - Can be either "Вчера я читал "Дэвида Копперфильда"" (i.e. "I spent some time reading "David Copperfield" yesterday") or "Вчера я прочитал "Дэвида Копперфильда"" (i.e. "read completely").
"I didn't use to eat icecream when I was a child." - "Я (обычно) не ел мороженного в детстве." (iterative -> imperfective)
Well, it's a bit confusing subject. I'll try to explain how it works:
Grammaticaly, perfective verbs express instant actions, which have no significant duration. But logically they still can have it.
"Я написал письмо за два часа". - The action "написал" has the duration "два часа". The preposition "за" means "in exchange for" here, so literally, it is "I wrote the letter in exchange for 2 hours spent."
At the other hand, imperfective verbs mean processes, that have some duration and have no "end point". But logically we can guess that "end point".
"Я писал письмо два часа, когда он пришел". - Here, the process was/had been going for 2 hours and then the action "он пришел" happened.
But if we erase "когда он пришел", the meaning of the sentence changes significantly.
"Я писал письмо два часа." - The process was going for 2 hours and... since the time spent is mentioned, then something happened after "два часа"? We have no clue what happened, so we can logically guess that the process reached its end point.
Imperfective + time and perfective + за + time are used in different contexts:
"Что ты делал сейчас?"
"Я два часа писал письмо."
"За сколько ты написал это письмо?"
"Я написал его за два часа."
"I have been to America" - "Я был в Америке"
"I have never seen this man" - "Я никогда не видела этого человека"
"The pupils have always enjoyed his classes" - "Ученикам всегда нравились его уроки (и сейчас нравятся)"
I think, in most cases "experiential perfect" should be translated with imperfective verbs, since no "instant action" happens here and no "end point" is reached.