intermittent service dropouts

We've been experiencing almost daily service dropouts for the past 2-3 years but now they are becoming a serious issue because our son is a bank auditor who works from home and the service blips cause serious losses of work for him. For security reasons, PNC doesn't allow saving work to his remote computer. Before anyone starts asking inane questions or making obvious suggestions like "did I remove any cables", here's a list of what's been done so far:

1. Comcast crews already have trenched in a new Commscope semi-rigid distribution U/G service cable with a Polyethylene jacket and a flooding compound. I designed   traffic management systems for the State of Md for 30 years, and I specified a similar 6 or 12-pair jelly-filled cable back in the days when T1 service was king. We don't want to see those crews again. We already had the EXACT same cable which was installed in 2010, and they cut that one and then split when they realized what they had done. We were without phone (including our burglar/fire alarm), TV, and Internet for a week, and received only a $37 credit to our next month's bill.

2. We have all new connectors and unused port 75-ohm terminators, installed by a Comcast Tech.

3. Our system uses the Commscope 8-port Zero upstream and downstream loss amplifier. The cable enters the house to the amp and then the signals are distributed radially to all ports in the house from there. In other words, the Gateway, an Arris 1682G, is essentially in parallel with the TV's.

We had one unused port with a terminator on the amp so I just connected that one through shielded coax to one of my bench grade Spectrum Analyzers, an Advantest R3641 with a range of 9 kHz to 3 gHz. I've chosen a center frequency of 471 mHz, which is Comcast's downstream for Channel 1. I'm seeing excellent signal levels, and I have screen captures that I can't post here, unfortunately. But the range is -27 dBm to -33 dBm, well within the operating range for the 1682G modem/gateway. Each channel display is level and the channels are uniform.

I have a Applied Instruments MDU, but I'm looking to buy a Sadelco DisplayMax 5000 with options 1 through 5 so I can analyze my system for interference sources. But here's my question:

When the service drops out we lose ALL services, including the TV. Based on the radial system design, this suggests that the intermittent drops are coming from a Comcast piece of equipment, not something local in our home. The TV goes away completely so we have to rely on off-the-air stuff and our phones for Internet.

Does my suggestion that the intermittent is with Comcast sound logical? If the TV remained in service, I would suspect that noise in our upsteam was knocking the Gateway offline. But that shouldn't kill the TVs, correct?

[Edited: "Personal Information"]