1) Anything in fair - excellent range is considered very good.
Get poor or low, or no signal then consider changing location of router.
However it depends on how good the receiver is as well in the Laptop/PC.
2) There are a few things you can do to improve bandwidth on a wireless connection - and disable any WEP or other none required features - disable auto speed. Set all on maximum and disable power save.
3) WEP is still a good enough - and to further this I use MAC address filtering.