Most, if not all of the illustrations I have seen regarding slab depressurization depict the intake near an outside wall. Would the system not theoretically be more effective to locate the suction at or near the center of the slab rather than off to one side?

Hi folks, First time posting here, I'm hoping those more experienced than myself would be willing to offer advice on my dilemma here. My son and I moved into this place about 3 years ago and I have been doing a lot of updating and remodeling. Happy to say I have learned plenty of new skills. Am now looking into what would be my most ambitious project, and am feeling up to the task, but my research has given me pause, specifically around the issues of foundations and frost lines-Which I know little about. The house is built into a slope, there is some exposed ledge in the basement and plenty of ledge directly behind the house. The first picture shows the whole back area of the home, the closed area on the left is a bedroom and is partially on the main foundation and partially on an added block foundation, as you can see in the last photo where the blocks appear stacked vertically. Building inspector never found any issue with this and the room appears to have stood the test of time up until now. The second to last photo shows the other side of the house where the porch ends. You can clearly see where the porch is attached here. Underneath the porch is a crawlspace that can be viewed through a basement window looking directly under the porch. The 2 middle photos show my attempts to dig down at the front and see how far the blocks go down. The only info I was able to gather is that it goes down at least 2 blocks here before hitting a sort of lip of concrete. If that's a footing, that's definitely not deep enough right? I basically want to know if this foundation is going to cut it to build on. I have the electrical out there already. The basement window would allow me to route HVAC to the room. The roof has held up fine obviously. All I would have to do is frame, insulate the crawlspace, ceiling, and walls. Is this doable? How do I find out if this portion of the foundation will support the added weight? I don't know if I can just rely on what that back bedroom addition's foundation looks like (if I even knew for sure) because it is possible that it was made completely differently. If anyone can share their thoughts, I'd be much obliged. I'm up here in cold New England, so I take it frost lines are an important part of this discussion.