Its The old landline if you use it you can get one to ten mbps. We got one mbps on or old verizon landline and they would not help us with getting fiber,so as soon as another supplier came when I asked them we climbed aboard

just add the cost to the house price and buy new the new owner may like it for a selling point

Need a lot of info what you want done size of house access in walls ect ect ect

You are lucky our verizon landline gave us one mbps or less for a long time one step above dialup it sure was a slow go until we switched to new provider it was like the difference between day and night. verizon is way behind time getting any fiber out and overcharging for landline phone to make up for it we will see what the future brings

Looks ok to me just use some automotive plastic wire cover and cover the exposed wire with a little dum dum to seal the ends. That is what I did a few years ago