If you look at enlace oculto you'll notice that I managed to add a delete relationship link.
It seems that when editing the template for your View output using Blocks, the Form block doesn't yet support inserting such links. You can insert a Classic block and then use the traditional Toolset Forms button (although it's an icon), which shows a more complete list of options, although the delete relationship link is still missing, and this appears to be connected to designing the template with blocks, and when editing the template directly (not with blocks) that link should be available. (I'm going to discuss with the developers about what is currently supported/expected.)
In the meantime, I inserted the link directly in the Loop Editor, where the Toolset Forms button did offer to create the link.
As an aside, you've set up your View to use a one column Bootstrap grid, which is a bit meaningless, you could likely have just selected unformatted for the output format, which would have involved simpler markup.
Turning to the link to edit existing relationships, here I ran into problems.
I tried editing what you'd already done, and I tried starting from scratch with my own forms and templates, and kept running into the problem that the required option was always greyed-out (screenshot).
I spent well over an hour trying that, and I've had to ask a colleague to take a look as I need to move on.
So I'm escalating this while waiting for feedback from my colleagues. They have access to your site.
Edit the relationship so that it includes a relationship field (possibly a dummy one) and make sure your relationship form includes the relationship field (maybe hidden by CSS), and then it should be possible to insert the edit relationship links.
With one proviso, namely that the output of your View, you are editing the template with Blocks, in which case the edit link seems to be missing, even if you use a Classic block to insert the link with Toolset Forms rather than the Forms block.
It should appear if you insert it directly in the output section of the View, i.e. the Loop Editor, where I inserted the delete relationship link.