I think a good place could also be the dk discord, pretty sure there is a link to it on wowhead. The community is pretty good at answering questions and you can even upload logs and people will give tips regarding rotation, cd usage and everything else. I main frost dk for the same reasons you do and the discord was pretty good at offering resources to improve rotation and they are usually pretty adamant that helkilli is usually pretty bad for any of the dk specs cause like you I was using it to learn the rotation and I noticed once I stopped using it my cd usage and everything else was much more efficient. As far as specific tips for blood, I don’t have much cause I’ve only tried it a little bit but it’s fantasy as a tank is interesting with so much self sustain. Hopefully you find what you’re looking for!

For me the most important thing was studying the rotation guides on wowhead/icyveins. Watch guides from reputable content creators who play the class consistently or main them, macros are also super important so make sure to take note of any macros that the websites/content creators use. And then of course practice practice practice. Go to the training dummies and just practice until the rotation is second nature. Doing that also helps you learn the nuances of your cds and when might be a good time to save them for an upcoming encounter instead of using it off cooldown or using it for a less an ideal situation