[Conch]

Grabbing a handshake doesn't always mean it's valid.
A method I used to use was to strip the capture file in Wireshark and check the EAPOLs.
That way, you know it's valid and can effectively be cracked.

I wouldn't bother cracking handshakes though if you only use Laptops, you'd need a rig to do it.
Otherwise it will run like a slug.

There are also WPA cracking services available, they'll do the work for you, you just need a small fee to cover electricity, time etc.

If the password isn't recovered, you pay nothing else.

Reaver is good, but it's not very effective as it was in 2011-2012.
ISPs have caught on and implemented strict locks on the manufactured APs (At least in here in the UK - It's TERRIBLE)

Having said that, a new tool was released recently called "Bully"
Which randomizes the pins it checks to confuse the AP, thus slowing or even preventing a Rate limit.

It comes bundled with Kali Linux and it's easy to make and install in BT5.

If you lose all hope, then you could always set up a rogue AP, Buy two Wireless adapters, one for the collection of packets from the rogue network, and the other for the Denial of Service (De-auth) of the main AP.

Don't give up though, from your post, it sounds like you're too far away
Get as CLOSE as possible, High RXQ = Less inteference = Good.
Low PWR = The closer you are.

Getting a PWR from just 70 to 65 or even 60 can make a difference from not being able to crack it at all, to cracking the key with Reaver or Aircrack.

If you're wondering which WiFi adapters to choose, the AWUS036H and AWUS036NHA are perfect adapters.

Hope this helps!