Is there a way for me to configure my wifi hotspot so that I can use apps such as IP webcam while the hotspot is the PC's only internet connection?
You need an intermediate wifi AP to which both android and your laptop connect. The integrated wifi hotspot functionality won't work as it does only forward the internet connection and hides the rest (it adds a new 192.168.42/24 subnet and does NAT internally).
Technically speaking, of course, there's a way to do it. But it requires root and you would need to setup the network by hand (iptables, ip tools required) and make sure that the app does bind to the wifi hotspot standard gateway IP 192.168.42.129 and that there are no firewall rules to block it.