Hello! :-)

Do you think it's safe to use version 1.3 in public modpacks? I think there's a lot of good stuff and improvements, but it's still beta..

I would suggest waiting for it to come out of beta first, I can't say if there is anything that could possibly break a modpack or a world. If you do update it make sure to note that everyone should back up their worlds before updating.

Yeah, I don't think it's a good idea to distribute the dev versions in modpacks. As it is still in development so things are subject to change at any time. That being said, you still can put it in your modpack, but don't be surprised if there are bugs