Hello! I'm so sorry the web build doesn't work on Firefox. We looked into fixing it but it's quite complicated and it seems likely we will never get it to work on Firefox for various reasons :-( Sorry about that. Web builds can be tricky and often come with issues.
With regards to the download crashing, could you let me know which file you downloaded? What was the executable called? Your error message mentions "Web_0.1.2" which is strange. Makes me think you somehow downloaded the web build so I just want to double check that. I have attached a picture with the correct download file underlined if you could let me know if that's the one you have.
Thanks for sharing the error message. I hope we can figure out why your download version crashed. Sorry for the frustration :-) 