the short answer to #1 is that it is possible but not at all likely for the same reasons Kevin outlines in his answer to the question you linked to, especially the fact that almost no ham radio operators transmit continuously... only when actually having a conversation, and only when it's our turn to speak in the conversation.
Answering #2, the directivity of the ham's signal: it depends on the antenna. If the antenna he has is just a wire or pole sticking straight up in the air, it's pretty close to 360° even. If it's any other configuration, it's stronger in some directions and weaker in others.
A note regarding interpreting your measured signal to noise ratio (SINR), it may indicate a higher noise floor where you are OR a lower signal from your carrier. Without measuring the noise floor and signal strength separately at a location that "works," it's difficult to understand what's "really" happening.
It may be (likely is) that the antenna configuration & power from it in your direction is just not strong enough for the service level expected.
Finally: go introduce yourself to the ham! Many of us LOVE figuring out stuff like this. It may be that he even has the equipment to measure your signal issues and help diagnose and get to a solution.
BEWARE: you may become interested enough to get a license and pick up a fascinating new hobby... if that happens, we'll be here to welcome you in :-)