What do you think of this one:
3a-There is this bar in my neighbourhood that will make a lot of my neighbours sad if it goes broke.
Can one use that? The bar does not go broke deliberately so I don't think it is really acceptable.
It's okay. In spoken English, this is probably how it would come out.
The problem is in managing all those little clauses.
In written English, there would be an effort to connect the pieces that refer to each other, rather than wait for the end of the sentence to hear that it's about a bar that ........ might go broke. The easiest way to do that is to move "A lot of my neighbors will be sad if..." to the front.
The sentence could be rendered like this: (if the "going broke" weren't so uncooperative, no substitution would be necessary, but you can hardly say "whose going broke would make us sad.") --
There's a bar in my neighborhood whose bankruptcy (closing / foreclosure) would make a lot of my neighbors sad
Furthermore, "There is THIS bar ..." is pretty much confined to spoken English, and casual speech at that. I wouldn't ordinarily say that at all, except as a joke.
I think the best way to frame the sentence close to the one you have printed in red is:
There's a bar in my neighborhood that, if it goes broke, will make a lot of my neighbors sad. (or "....that, if it goes broke, a lot of my neighbors will be sad.") I would alter both of these for publication.
And this theoretically shifts the meaning a little (not in practice, but in principle.)