Conditonal tense with conjecture regarding the past

[cmon]

The Clarks must have had their dinner party last Friday.
Los Clark habrían tenido su cena con invitados/convite el viernes pasado.

The guests were probably boring and the food was probably not very good.
Los invitados serían aburridos y la comida no sería muy buena.

I wonder if the wife knows that everyone thinks she is a lousy hostess.
Sabrá la esposa que todo cree que ella es una anfitriona terrible.

There were probably about twenty people at the dinner party.
Habrían unas veinte personas en el convite.

They were most likely drunk by midnight.
Estaríán borrachos por medianoche.

Might Sara have known that she wasn't invited?
Sabría Sara que ella no invitaron?

Her ex-husband probably told them not to invite her.
Su ex marido les diría no invitarla.

If she had attended the dinner party, he would have had to talk to her.
Si ella asistiera a el convite, él habría tenido hablar con ella.

He would have hated that.
Él lo habría odiado (eso?).

I hear that he has a new girlfriend. Could it be Julie?
Oigo que él tiene una nueva novia. Será Julie?

I don't believe that Julie was at the dinner party.
No creo que Julie asistiera a el convite.

Marie would have told me if Steve had brought her.
Marie me diría si Steve la trajera.

Julie might be too good for him.
Julie sería demasiado buena para él.

Could Julie and Sara have ever met?
Se conocerían Sara y Julie?

They must have the same lack of judgement about men.
Tendrían el mismo falta de juicio sobre/con respecto a los hombres.

I'm sure that I was invited to the dinner party.
Mi invitación se perdería en el correo.

I wonder what time the dinner party ended.
Qué tiempo sería cuando el convite se terminó.

It was most likely way past my bedtime anyway.
Sería la hora pasada de me acuesto de todos modos.

[Tomisimo]

While you are probably trying to practice the conditional, I think I'll be of better help if I just translate each sentence how I would say it in Spanish and let you draw the conclusions. I translated "dinner party" as "cena formal", if you're going to repeat it in the same text, you should use "cena formal" the first time, and any subsequent times just use "cena". Another translation could be "fiesta".

The Clarks must have had their dinner party last Friday.
Los Clark debieron haber tenido su cena formal el viernes pasado.

The guests were probably boring and the food was probably not very good.
Lo más seguro es que los invitados eran aburridos y la comida no muy buena.

I wonder if the wife knows that everyone thinks she is a lousy hostess.
¿Será que la esposa sabe que todos piensan que no es buena anfitriona?

There were probably about twenty people at the dinner party.
Probablemente hubo unas veinte personas en la cena formal.
Probablemente asistieron unas veinte personas a la cena formal.

They were most likely drunk by midnight.
Lo más seguro es que para la medianoche todos ya estaban borrachos.

Might Sara have known that she wasn't invited?
¿Sara sabría que no estaba invitada?

Her ex-husband probably told them not to invite her.
Su ex-esposo probablemente les dijo que no la invitaran.

If she had attended the dinner party, he would have had to talk to her.
Si ella hubiera asistido a la cena, el habría tenido que hablar con ella.

He would have hated that.
Le hubiera incomodado tener que hacer eso.
A él, le hubiera desgustado eso.
A él, le hubiera molestado eso.

I hear that he has a new girlfriend. Could it be Julie?
Me dijeron que tiene otra novia. ¿Será Julie?

I don't believe that Julie was at the dinner party.
No creo que Julie fuera a la cena formal.

Marie would have told me if Steve had brought her.
Marie me hubiera dicho si Steve la hubiera llevado.

Julie might be too good for him.
Puede ser que Julie sea demasiado buena para él.

Could Julie and Sara have ever met?
¿Será que en alguna ocasión Julie y Sara se habrían conocido?

They must have the same lack of judgement about men.
Deben tener la misma falta de juicio en cuando a los hombres.

I'm sure that I was invited to the dinner party.
Estoy seguro que estaba invitado a la cena formal.

I wonder what time the dinner party ended.
¿A que hora habrá terminado la cena formal?
Me pregunto ¿a que hora habrá terminado la cena?

It was most likely way past my bedtime anyway.
Seguramente terminó mucho después de la hora a la que me tengo que acostar de todas formas.

[cmon]

Was everything I wrote not accurate or is the conditional just not used much with past conjecture?
Grammar book says:
The conditional is used to communicate probability/conjecture referring to past time or activity with decir, estar, haber, ser, and tener.

[Tomisimo]

Your grammar book is right, and the conditional is used to communicate probability and conjecture. But it's not the only way to communicate probability or conjecture. While it is most definitely used, I wouldn't say it's all that common. I tried to translate each English sentence into the most common/natural way of saying it in Spanish. I used the conditional in some but not all of them, which should give you an idea of how common it is.

[cmon]

Can you give some example sentences where the conditional/past probability/conjecture combination would most likely be used?

The book doesn't go into much detail on the subject. Found it all rather confusing, as you can see from my post.

[Tomisimo]

Ooops, been a month and I didn't see this. I usually hear the conditional used for conjecture in questions like this:

¿Iría a la tienda? = I wonder if she went to the store.
¿Pintaría su cabello? = Do you think she (would have) dyed her hair?

[cmon]

David olvidaría contestar a mi pregunta?
No, él no olvida contestar nunca.