I'll try to answer at least some of your questions:

1. Could "I'd been certain" is translated as "je m'étais senti certain"?
That doesn't sound right in French.

2. Could "la chance n'était pas de mon côté" have been translated as "les chances n'étaient pas de mon côté"? 
I don't think so. "Luck" is la chance, that doesn't work in plural.

3. Could "Nous serions ensuite allés dans sa nouvelle maison" be translated as "Nous serions allés ensuite à  sa maison neuve" ? Queries here about  "dans sa nouvelle maison" vs "à  sa maison neuve" and also about the position of "ensuite" in the sentence.
The standard placement of adverbs is right after the first conjugated verb. So I'd have to say no to this one, too. Using the prepositions dans emphasizes that he entered into the house. Whether you use à or dans depends on what exactly you want to say. And regarding nouvelle or neuve, that depends also on the context. In general, one uses nouveau/nouvelle unless it is important to stress the fact that something is brand new.

4. Could "que j'aurais fait meubler au préalable" be translated as "que j’aurais fourni en avance"?
No, I don't think so. The verb fournir primarily means "to furnish", "to provide".

5. Could "au fil des ans" have been translated as "pendant les années" ?
Au fil des ans is a bit poetic to say, "over the years". Here, I would say that pendant is probably a synonym.