about subjunctive

Hola Ελισάβετ

1/ With "el hecho de que..." we can use both the indicative and the subjunctive. Using the indicative "el hecho de que no hay..." would mean that the speaker is presenting that bit of information as "new"; This is less common though; generally you will see "el hecho de que" followed by the subjunctive because with this information we normally talk about something that is "already known" by the speakers, as if it was background information:  "el hecho de que no haya...". This is the case in our writing challenge.

2/ hasta que pueden dejar la casa de sus padres; this bit of information seeing it detached from the previous clause sounds as a future event as you say, but if we have in mind the whole sentence, it is saying:

"y sus planes de formar una familia van posponiéndose, hasta que pueden dejar la casa de sus padres"

What this part of the text is referring to is something that actually happens, it is describing the situation for young people in the present time, and that is that "they postpone their plans to form a family until they finally leave home" - we need to see the whole thing as something "currently happening". 

Have a look at this other sentence (not from the writing challenge but a new made up sentence) where it is definitely expressing a future event:

This use of subjunctive in "te lo diga" is clearly a future event. The fact that we are using the imperative in the main clause "no cruces" is indicating that it is something still to happen. 

If we modify the text from the writing challenge and make it the subjunctive instead of the indicative, we could say for example:

Here, to make it a future event I changed the verb in the main clause to a future "se irán posponiendo"; this then triggers the subjunctive in the clause with "hasta que".

Sorry about the long explanation - it is a tricky one.

I hope it clarified it.

Saludos y ¡felices fiestas!

Inma