If you're no longer employeed by the selling company, it would seem that you have nothing to gain by signing.
But it's the first time I'm asked to sign one of these things and some of the things I'd be agreeing to doesn't even sound like it's in english. I don't want to inadvertently sign over any side project I was working on in that time or IP for the industry I was working in or even future IP as some of it seems to be worded without time constraints. But take all that with a grain of salt, no legal background.
The sale of the business is predicated on all former employees signing the deed.
What they're trying to guard against is an Oculus Rift type situation. You signing a clear statement of "mordrax has no further interest in any IP that's part of this deal" is probably good enough for them. You don't have to sign exactly what they put in front of you, especially if you can't understand it.
If you're worried, get an attorney (who understands software IP) to read it. Get the company to reimburse you for the attorney fee (and maybe your time).
Turn it around and tell them your needs: you don't want to lose rights to your own work. Leave at that at first, and see if they come back with anything, such as a list of the specific works they want you to disclaim prior to their acquisition.
You get the open end, not them.
And charge them for laying you off, I assume you don't have equity that will act as any kind of redemption in the sale.
IANAL, but I suspect a key detail here is that you are hiring the lawyer, no your former employer, because that's crucial to having the attorney bound to represent your interests.
But again, IANAL, so I could be totally wrong.
The usual way to deal with side projects is to specifically list the things you own and want to protect that should not be included. This is often a very small set of identifiable things. If you're worried this might be an overly broad set, then you can go the other way and try and list all the work you did while there. They will then need someone to review it to make sure that's everything they need, and then the buyer will need to review it to make sure that's everything they want. If this is an asset transfer, they will also need to make another list which is the things they are specifically not buying. So you make things more complicated doing it that way, but it's certainly your right to do that since they don't have an agreement with you already. Their fault for not giving you something when you started.