It sounds like you are in the right place for learning jazz standards and tunes form the Great American Songbook.
Here are the courses and resources that I would recommend for you:
We have a couple of vocal piano courses taught by Lyndol which address vocal accompaniment and also some vocal exercises:
You might like to check out these vocal themed seminars, there are 13 of them in total which delve deeper into different vocal topics:
We have a gospel blues course taught by Davell which covers some interesting accompaniment principles. The final lesson of the course shows the live accompaniment of a gospel singer. Check that course out here:
You can find lots of articles and related lessons here on vocal accompaniment:
We are soon building out a new subcategory for vocal-play-a-long tracks. It’s been on my to-do-list for some time and I will get around to that shortly.
In addition to the vocal lessons, here are our index pages so that you can browse the rest of the courses and lessons on the website:
Let me know if I can help further and enjoy the lessons.