Wow!! Renata, I am so proud of you.

Your bat looks fantastic and I'm loving the metalic thread. Every corner looks crisp and clean! You really did GREAT. Thank you very much for the compliments, but I can't take all that credit my friend. I think digitizing has been in your blood all along. You just hadn't let it out to roam and play yet! I just encouraged you to let it out.
As for thread, the answer is whatever you like best. Personally, I like my satin stitches to be full and filled so that there is no applique fabric peaking through, but it's your design to choose what pleases your eye the best. My commercial machine does not like Isacord so I don't use it. I use Maderia Polyneon (more colorfast than rayon) or Rapos thread 40 weight. There are others that I use as well depending on the color that I need.
I can't wait to see what you do next now that the Genie is out of the bottle!
WARNING -- Digitizing is highly addicted and compulsive disorders can and do frequently occur causing episodes of dreaming about creating designs, modifying designs, and generally keeping your mind occupied at all hours day and night with the 'what if' factor! The best medicine for this is to frequently spend time at this new craft and stitching out newly created designs on different fabrics to see and learn how the same design can and will look different depending on the fabric/stablizer chosen.