kggr ji
I have wrestled with this controversy myself for some time and have only recently come to my conclusion (that is, my conclusion for the moment!). Maybe hearing some personal account will assist you personally, too.
No matter the authenticity of the entire Dasam Granth, the general consensus is that it is highly probably that some of the texts were written by Guru Gobind Singh ji. That includes Jaap, Chaupai and ten sawaiyas.
Furthermore, they do not appear (to my understanding) to conflict with teachings from Sri Guru Granth Sahib Ji.
For a long time I omitted Jaap, Chaupai and Ten Sawaiyas. Partly because when you're learning it's a LOT to take in, especially if you want to read your nitnem every day, and they make the process long in the beginning. And partly because I'm not sure about Dasam Granth. And partly because it made more sense to me to read nitnem as presented at the start of SGGS
But I have recently started including them, and they are very lovely and powerful.
So I would say, if you're unsure, focus on the SGGS bania, don't worry about the others from Dasam Granth -- they'll fall into place if and when the time is right, like they did for me. Read about them, read them, come to your own conclusion.