1) The Priests of both the SSPV and CSPV have always flown on airplanes, and never stopped flying when the intrusive TSA procedures came out.
The NUNS stopped flying at that time, and for that reason, but the Priests never did. And within the last couple years the nuns have begun flying again too.
2) The CSPV does have one priory outside of Round Top, and that's at Oyster Bay. 2 Priests and one brother live there currently. They will likely open one in Minnesota at some point.
3) One of the CSPV Priests has been suffering from health issues the last few years, issues that cause him to be unable to travel long distances on his own. As a result he is assigned to mostly take care of Round Top on a permanent basis, which works out well given he shouldn't travel a lot.
4) Almost all the CSPV Priests travel on most weekends, and Bishop Santay ofen does too.
5) As they have gotten more Priests they have also opened more missions. Consequently, although their supply of Priests has gone up, the number of places they serve has too, so they aren't able to always give more Masses/attention to their existing chapels.
6) Although all but two of the CSPV Priests LIVE in Round Top technically, often Priests are out at one or another chapel at times other than weekends, for funerals, sick calls, summer Catechism, etc.
7) The rift between Round Top and Cincinnati has largely healed, and Fr. Jenkins has been in Round Top to attend the last few ordinations, and the bishops have been in Cincinnati to do confer Confirmation recently.
8) The issue with setting up priories wherever you think is required, is that normally when a priory is set up I think it's expected that the chapel with the priory largely, or maybe even entirely, support the Priests who are resident there. Some of the CSPV missions can barely afford to fly the Priests in, and definitely couldn't provide them with full time financial support, health insurance, housing, house maintenance costs, etc.
9) Black Eagle MT, White Bear Lake MN, and Cincinnati OH are the three churches with resident Priests of the SSPV. The CSPV help them when needed. It's important to note that when there are sick calls in Mission chapels, sometimes those missions aren't very close to one of the three resident SSPV Priests' chapels, meaning that these Priests might have to fly to get there too.
10) Bishop Kelly is indeed sick, and has been for a long time. I was told by a Priest that Bishop Kelly comes from a kind-of "sickly" family, and for much of his Priesthood has been ill with one thing or another.
He has some type of cancer I think, along with various other things. In all the years I have attended the SSPV/CSPV he has been sick and I've never known a time where he has travelling on a Mass circuit at least in the years I have attended their Masses. It does seem odd that Bishop Dolan, Father Cekada, and Father Collins are all gone but Bishop Kelly with his years of sickness is still with us.
11) I too have heard that St. Teresa in Cleveland is dying out, as the parish is mostly made up of older people. I'm not sure why that is, but I could hazard a guess that maybe younger people with young families who start out at Cleveland eventually would want to move to Cincinnati since Father Greenwell and Father Jenkins have a K-12 school there.