I don’t think we are actually disagreeing.

I think we are talking about two different things.
The OP asked if a venial sin can ever in certain circumstances be a mortal sin. The answer is no. You need grave matter for a sin to be mortal. Yes, consistently commiting venial sins can
lead to commiting a mortal sin. But that’s different than saying a venial sin can
be a mortal sin in certain circumstances. Which is the question the OP had.
Getting frustrated can lead to all those other things you mentioned, which ARE mortal sins. But getting frustrated is not in itself a mortal sin and never can be. That’s all I’m talking about.