Hey there Samfent17
Sorry to see you're running into so many issues with your DLC! For DLC purchases, those are only eligible for refunds if you purchased as a bundle- DLC purchased separately is typically not eligible for a refund. You can read over the refund eligibility details in the help article here for more details on this.
However, we can definitely troubleshoot these issues with you and try to get everything working properly. Could you provide a bit more detail on what happens when you try to build something?
For the crashing and freezing you're seeing, please run a DxDiag and attach that to your post so we can look into this further with you.