So for about a month I have been trying to get these blockstats to work in my personal resource pack, the models for the blocks work if you have them by themselves and I have optifine, but there is something wrong with the codes.
No, I just open it with notepad because my computer can't open .json files.
Get Notepad++ (It's freeware) and set your computer to open them with that.
Also, make sure you have all file extensions visible to make sure it's "grass.json" and not "grass.json.txt". The added file extension WILL cause the file to simply fail.
Additionally, running your file through https://jsonlint.com/ to make sure that it's valid is a good idea. If it isn't, it might give you a hint as to where you made a mistake.
Beyond that, it would help if you'd post the files themselves and not screenshots. Likewise, post a session log from a session where you had the pack active. That'll help to narrow down the problem. I hope that helps.
Sorry, I didn't see the pastebin post. I just threw the codes into JSONLint and the grass and pumpkin codes are not valid. I'd guess that the problem for the grass JSON is that you've got an extra comma at the end of the snowy=false variant. For the pumpkins you seem to be missing an end bracket for each variant. As for the end stone, I'm not sure what's going on there.