let go of wanting to change the past in my meditation practice
The scripture Iti 74 says a child who practises Dhamma is superior to parents who do not practise Dhamma.
You cannot change the past.
However, you can clearly comprehend the immoral &amp; wrong actions of your parents and then aspire to live in the opposite way.
You can aspire to not be like them, which means you treat other people in the manner you yourself wished you were treated.
In other words, you aspire to never ever repeat your parents mistakes &amp; errors.
If you have some care for your parents, you can dedicate your efforts to your parents, as though to make merit for their sins.
As for 'gratitude to parents', the scriptures say children honor &amp; venerate their parents who have been compassionate (rather than cruel) towards them. Refer to Iti 106.
Also, refer to my answer to this related question.