"Por último"

"Por último"
 

This is a unique phrase that can be used in the past and future, is that correct? As in the phrases "Last, I did ________" and for the future "Last, I will__________"
Past:
Fui a la tienda, después, yo corrí, por último, yo lavé los cuencos.

Future:
Hice la maleta, después, conduje al hotel, ahora, estoy comiendo en el hotel, por último, yo desharé la maleta

Would that all be correct? I just learned "deshacer" today by the way, so please correct me if my usage was incorrect.

Also: can it be interchanged with "más tarde" for the future?

"Para empezar" ([to begin] for one thing) I would translate "por último" as "finally" or "lastly", and so, the same way you can use these English words, you can use "por último".

Y por último quiero decir que... = and finally [or lastly], I would like to say that...
Yes, you are right! :)

(One thing, I would personally not use "yo" in the Spanish sentences, unless I wanted to make really emphatically clear that I am referring to me.)

In my understanding.

Por ultimo could be translated into of the English as The end, the last.