While there is nothing in the rubrics of Mass that call for making the sign of the cross at any point during the communion rite, there is also nothing distracting or showy about it to call for discouragement of this fairly common custom. If someone feels personally compelled to do so out of reverence for the Eucharist then they should feel free to do so but at the same time no one should compel another person to do so since it is not mandated by any Church document or authority.
I haven’t the foggiest clue as to why someone would “hold up the chalice of blood before drinking towards the tabernacle.” I have no idea if that is the custom from the culture they are from or if its just some form of personal reverence the individual chose to enact. Where this differs from situation #1 is that, at least in the USA, there is no custom of doing this so its strangeness could become a distraction whereas a simple sign of the cross is fairly widespread and so innocuous that most wouldn’t notice someone doing it. And, obviously, there’s a danger of spilling some of the Precious Blood if the chalice is fairly full and the person is not careful.
If any members are aware of a culture or Eastern Catholic Church where the raising of the chalice by communicants before reception is a custom, please PM me and I’ll update this answer.