the time issue isn't really significant. A lot of recruiters do this to try and push you into accepting something quick, but if you need 3,4,5 days etc, it should be fine.
At many corporations, jobs sit empty for MONTHS. A good candidate is worth waiting for the accept, especially if they made you an offer.
On the salary bit - This happens a lot. What you should know, is that when you go back with the salary bit, the recruiter you're talking to will tell you if what you're asking for is not possible.
If it's a 3rd party recruiter doing the hiring and communication, they may also lie and say that it's not possible, when they just want to close a deal quickly.
You can see an example of this when you talk to some recruiters, you throw out a salary expectation and they seem to always magically push back to about $5/hr short of it, no matter what the amount is ;) (in the US, anecdotally, that's been my experience with recruiters with a certain accent, but i don't know why)
I would say, hey I was looking for closer to this number. Can you ask the hiring manager if they can come up to this?
The recruiter isn't going to want to blow a deal, especially if it's not a huge sum of money. In the end, 5k-10k is a rounding error in a departments budget; there are some corps that have set caps on pay, or that won't negotiate as a way of keeping 'equality' and ensuring people in a given role are near the same paygrades, but if it's an amount that's commonly achieved for your role or industry you should ask.
Just try to get everything you are asking for, together in one lump sum push, you don't want to go changing the requirements you have after you've stated them.
If you're asking for too much, they will tell you they can't come that far up.
Don't phrase it too strongly - if you say "I can't do this unless I get $10k more", it will sound weird as if you're saying no, when they realise they can't do it. So maybe "I was hoping / expecting to receive an offer closer to X".