Prayers and support are with you with the passing of your step father.
Yes, thankfully he did not linger--- that is a Blessing in itself.
Gina, you made the right choice for yourself at the time regarding saying your final good-byes. Please do not beat yourself up over it now---you did what you thought was right. Certainly you might have "guilt" about it after the fact, but really you shouldn't. It is a personal choice for everyone----and one that once rthe choice is made, cannot be changed. Accept that your choice was made with the very best of intentions for your emotional well being at the time and that your step father would understand this; he would not want to cause his family undue pain and suffering. There will very likely be many times ahead for you with regrets for things not done, or for things done that shouldn't have been done---suffering the pains of sadness for the past, the present, and future. That will all be part of your normal grieving process. Understand that you will "do the best you can" as these reminders and thoughts come to you. It is very important for you to be "good to yourself"....we cannot change things, we can only come to accept them.
Reach out to your Mother for her care and support---in return, she will also reach out to you. Together you will remember and all the wonderful things about your step father.
Share your feelings freely--that will help you to be healthy in your healing. So many of us have suffered such great losses---know that we are here for you. Our thoughts are with you as you go through this time. And remember----your step father is also with you.
"For every Joy that passes, something Beautiful remains"