Is this chapel actually some type of shrine, or miraculous building? I only ask because I've been there and that chapel was no bigger than a 3 car garage. While I loathe the sspx's financial focus, and give-us-your-property-and-we'll-give-you-a-priest attitude, I don't see how this chapel is a long term solution. It's just so small. In this case, it might be wise to sell it (assuming there's no miraculous nature to it), and build something bigger.
I'm not sure what you're talking about. That church building is much bigger than a "3-car garage". Nearly 200 people assist at Mass every Sunday. It's tight, and a fair number stand in the back. It's bigger than 75% of the SSPX chapels that I've been to (and I've been to a lot). Perhaps you are confusing it with St. Peregrine's in Cleveland. He also built an 8-classroom school (to accommodate 8 grades) on the property and has been running it for about 15 years now.
Beside that, it's not about the buildings, but the people, the souls. But the SSPX cares more about buildings. Father Carley's intent was that the people for whose spiritual needs he has cared for during the past 40 years would be taken care of. But it seems like you have the same attitude as the SSPX. You hardly "loathe the sspx's financial focus", as you put it but seem very much aligned with it in your thinking. Father's intention isn't to have them sell it, but to care for the faithful there. He could sell it himself, retire (nobody would blame him), and tell people to go to the SSPX chapel. But as far as I can tell, he intends to care for the faithful until his dying breath (... or he can no longer physically do it). He has to use a rail to help him genuflect, and yet he'll kneel for 20 minutes leading the Rosary. He broke his hip a few years ago and came back within 6 weeks (despite Dr.'s orders). While he was convalescing, he asked the SSPX to send someone to fill in, and they hemmed and hawed. Father finally threatened to pull the property from his will, and they finally sent Bishop Tissier on Christmas Day that year to do damage control. But you can be sure that without such threats, they'll not really care.
Also, while the SSPX chapel closed up shop during COVID, Father Carley stayed open and there were overflow crowds of people displaced from the SSPX (and even the Motu) Masses in the area that had caved and shut down. Despite the fact that Father Carley himself is "high risk" due to his age, he kept offering Mass and hearing Confessions every day like he always had.
If the building gets too small to accommodate the faithful, simply have 2 Masses. Father Carley, now in his mid-80s, just can't do it ... although even then he regularly drives (or, rather, has someone drive him) to Wheeling, West Virginia, to offer Mass for a small handful of souls there.
And that kind of missionary spirit is what used to drive the SSPX of old. They offered Mass in hotel conference rooms and barns and everywhere else. But forget that now. Let's build $50- and $100- million dollar structures ... at the expensive of all the other faithful around the country. SSPX have lost their way.