Yes, i know. I bought 25 X 16G for $80 yesterday. I Just wasn’t sure about this model in particular.

I have 3 servers. 2 R620 and 1 R630. The fans are loud before post but after they are quite quiet. I have them in my garage so noise/heat is not an issue for me nor it the power consumption. If I were in EU that would be a different conversation. I run Proxmox on them in a cluster and nested 7 ESXi “servers” along with a bunch of other LXCs and VMs. I don’t think it’s a huge investment for less than $400. You could flash that H710p to IT mode and have the TruNas ( or any other one ) manage your HDDs.
Also at the same time reduce the fan speed. You can have so much fun and functionality with it. Keep in mind the everything resides on 1 physical server and you will not have any redundancy. However, Proxmox, ESXi and the like need at least 2(+ witnesses) or 3 to allow you High Availability ( HA ) and to be able to move your VMs. Having 1 hypervisor on the bare bones and nesting ( installing other Hypervisors) under it you could create a hell of a lab.

It doesn’t matter what cable you use on the inside of your house ( LAN) You will not change the speed of your Internet (ISP WAN) unless they change it. That being said, what you will change by upgrading the cables is the speed at which 2 or more of you cabled devices ( NAS, computer, servers etc.) communicate. As far as the Ethernet cable is concerned, I wouldn’t spend money on anything but CAT 6 maybe CAT6A. The rest of them are not worth it. If you want a better cable for really short distances use DAC cable SFP+

Some things sound off to me. 1 The ISP wouldn’t send someone out since the previous tenant owes them money. That means that it had internet there before. This means you do have the connection from the ISP to your house. 2 Not all the ISPs have modem/routers that you have to plug into an Ethernet cable. Some have the COAX IN and Ethernet out. 3 where is the wire from your wall RJ45 terminated? Meaning - where does it go? Do you have a network closet that you haven’t seen yet? Some pictures would really help troubleshoot. Check your attic, closets, garage for a “ box” in the wall with some Ethernet cables, coax cables.