Need help: Bridge mode vs. "Share a public IP address" or "Distribute a range of IP addresses"

My Airport Express is connected to a cable modem to create a wifi network, however, when set up in Bridge mode as directed, my MacBook Pro and my iPhone 3G are able to connect to the network, but my girlfriend's PC and HTC are not. When I change the setting to either

"Share a public IP address" or "Distribute a range of IP addresses" all devices are able to connect. Given this, I have several questions:

1) Do I need to run the Airport Express in Bridge mode and if so, is there anything I can do to allow the PC and HTC to connect?

2) If I don't need to run it in Bridge mode, which option is better: "Share a public IP address" or "Distribute a range of IP addresses"?

3) Will I run into any double NAT or any other problems with either of these settings and if so, is there a way around it?

4) Should I take anything else into consideration if using either "Share a public IP address" or "Distribute a range of IP addresses"? Are there any other settings I should change or set-up?

My set-up info is as follows:

Version: 7.6

Connect Using: Ethernet

Connection Sharing: [see above]

Configure IPv4: Using DHCP

Radio Mode: 802.11n (b/g compatible)

Wireless Security: WPA 2

Channel: 11 (Automatic)

MAC Address Access Mode: Not Enabled

Thanks!