Been looking around in my routers settings for something that even comes close to limiting bandwidth on a specific port, or mac address, but the only thing I can find is priority settings like "Low, Normal, High, and Highest" I did however see this:
I am not 100% sure if I can specifically set bandwidth limit per port or mac address, cause I don't see an option to do that, so I presume it just limits the whole network as one...
Depends what you mean by bandwidth. Most people mean a cap on bytes transferred over a period of time. No router that I know of has that feature most because where would it keep all records for how much data each thing transferred last hour, last day,last week ? Device that do this generally are servers that have harddrives.
Now the one a router can do is limit the RATE a device can transfer. For example you can say you can only download 1mbit/sec. This is called traffic policing or traffic shaping. Most devices have what yours does which is a form of qos that in times of over usage certain traffic gets priority but it does not hard limit anything.
DD-WRT firmware has some ability to limit traffic. You would have to go to a commercial router if you wanted to do advanced traffic management and even those cannot do bandwidth capping type of things since they too do not have hard drives
You can't with the current software. You would have see if your router is on the list of routers you can update with dd-wrt firmware. If not you need buy a new router...but you first have to really determine what you are trying to accomplish
Use QOS (Quality of service) click the set QoS rule button then select a range of the ip adresses e.g.(192.168.0.1 - 192.168.0.200) set Wan to Lan "Minimum Guaranteed Rate" 20% and a second rule with Lan to Wan "Minimum Guaranteed Rate" 20%.
The setting are based on my router not a Netgear so ip addresses may be different or you may want to set 40%.
And from the help text on that picture it looks like you may just need to select the MAC addresses not a ip range. Maybe you can post a picture of the rule page.