Just to make sure I understand the situation..
You have a new AC model extreme?? Running 7.7.1?
Are these the correct things to be doing? I've included screenshots of both the NAS port errors as well as an example of a port entry in the AirPort utility.
Your port forwarding looks fine..
This is pedantic but can you change the variable name.. eg.
Harrison HTTPS
I know will fail in most routers.. the space being illegal.. I know apple have this strange naming convention.. but it just gives me the heabie jeabies when I see it. You can call it HHTTPS for example .. anything but no spaces and pure alphanumeric.
BTW you never need block out a private IP address.. it is not routable.. I can tell you my computer is here.
There is absolutely no way you can connect to 192.168.2.103 or 10.0.1.101 or whatever private IP is.
When hovering over the red buttons, it reads "Port # is already in use on your router, or your router is not compatible with the UPnP-IGD/NAT-PMP protocol"
Your last few lines are the most distressing..
Lacie being a more Mac orientated product has included NAT-PMP protocol in the NAS to open the required ports.. automatically in an apple router.. that means it should be able to work without intervention.
Ports cannot be opened if they are already allocated. which is what the error message means.. already in use.. they are in use because you allocated them..
I suggest you reset to factory the AE.. start up a single computer.. leave everything else off.. Do a basic setup of the AE just to get you network and internet access.. Then power up the NAS .. and see if it can open those ports automagically.. If not then the AE is simply not going to work at this firmware level.
BTW.. there is no doubt the 6.3.1 utility on Mac is problematic.. Apparently the iOS one is much better.. or even 5.6.1 utility on a windows PC. If you have an iphone/ipad use the airport utility app and do the setup from there.. rather than a mac.. it has more chances of working.. maybe.
You have an express.. this sounds odd but please change the firmware in the express back to 7.6.1 (I don't use express so I know less about them). Set it up as router in place of the extreme.. and try the NAS again.. you might need to buy a switch to do all this. But it should work if you do it via the iOS device.. well worth a try too and see if the earlier firmware can auto allocate ports via the NAT-PMP or even if that fails by manually allocating them.
Or the other choice is a non apple router for now.. and put the Extreme in bridge .. ie take away all NAT responsibility from it .. use your non-apple router firstly try by upnp and then manually forward the ports if you have to..
Hope something in there helps.