>>1 Unfortunately, there is no way to guarantee 100% uptime with any connection, let along a free one. The recommendations of wifi boosters, or, if necessary, a long range antenna as Seattle suggested are probably your best options. In terms of hacking into wifi, it is possible, but difficult with the security put on most wifi networks currently. You would need to forcibly disconnect someone from the network, then intercept their packet when they try to reconnect, and crack the password contained within. Whilst this is possible, it is difficult, and you would have to learn how to perform all those steps. I recommended just going for a booster.
