First of all reciting from the middle of a Verse doesn't make the prayer invalid neither for the fad (who prays alone) nor for the imam and those who prayer behind him in congregation!
As an Introduction: You should know that the fatwas or opinions which are qouted later here can vary because some scholars are considering it more basically from fiqh point of view and other's are analayzing from quran recitation point of view: So if you want to know it from a fiqh point of view those opinions which i refer as in general are the ones who come from faqihs. But if you would like to know if from a recitation point of view what you did is ok you should ask a scholar who teaches quran recitation!
- Some scholar say it's forbbiden to do this.
- Some other's do explain cases where it is forbbiden: If you interupt a Verse and a meaning gets lost which refer to an earlier part of the Verse.
- In general one could say doing this isn't preferable but allowed!
As Allah says:
So, recite of the Quran as much as may be easy for you”
[Surat al-Muzzammil (73:20)]
This doesn't fix an amount as Surah or a Verse or a part of it?
And as an other evidence we have:
Narrated Muhammad bin Ka'b Al-Qurazi: "I heard 'Abdullah bin Mas'ud
saying: 'The Messenger of Allah (ﷺ) said: "[Whoever recites a letter]
from Allah's Book, then he receives the reward from it, and the reward
of ten the like of it. I do not say that Alif Lam Mim is a letter, but
Alif is a letter, Lam is a letter and Mim is a letter."
Which shows that even reading a letter is ok!
For more details see this fatwa and an other a bit different fatwa in Arabic!
Additional information about Waqf and Verse counting!
And at least i'd like to let you know that there's no fixed rule about the number of Verses in the majority of Surahs (Suwar) as this was made by ijtihad of the Sahaba and some tabi'yn as i mentioned in my answer on How many ayaths are there in Al-Quran? there are different counts of the Verses in the Quran!
And even about the waqf in general scholars say there's no waqf lazim in Quran, as for some reading there might be a waqf lazim in a place where in an other they don't even have waqf!
And Allah knows best!