To answer the OP's first question, I use an SGS2 as a WiFi hotspot to connect my TF300T when I'm away from home and so far it's been rock solid. Tested it in a car ride for over 100 miles outside major citys and it did a good job. Even streaming video on a sports website worked fine.
For the second question. It's fairly easy. First set up the hotspot in the phone by going into Settings/More.../Tethering and portable hotspot/Configure portable WiFi hotspot. Here you enter a Network SSID name, a WPA2-PSK key and press store/accept/or wathever ().
Now turn on Portable WiFi hotspot é voila your phone is ready to make connections with WiFi capable devices.
On the tablet under WiFi in Settings you will see a new WiFi access point with the SSID name you entered in the phone. Tap it, enter the WPA2-PSK key you set in the phone and tap connect. After about 15 to 20 seconds the tablet will be connected to the phone.
Hope this helps.