While that is disappointing compared to the single figure gaps in other polls, it is worth bearing in mind that the ICM polling is the most heavily weighted to account for demographics seen as less likely to vote. I think it is wrong, because a lot of those demographics are much more likely to bother voting this time. Also, this poll was reporting a 20 point lead for the Tories only a week ago, so a reduction to a 14 point lead is still a good sign of the direction of travel.
I don't follow the minutiae of how individual polling orgs weight their samples so will take your word for it of course. Absolutely correct to compare like with like - the narrowing of the lead here reflects that of the other polls from the last few days so we know something is going on.
I suspect the reputation of pollsters will take another knock in this election. Reports from the doorstep seem to say a fair number of trad labour voters are 'undecided'. Which suggests that what happens in the last 2 weeks will be quite key, and pollsters will find it very hard to track what's happening. First time/young voters are also a bit of a wildcard in terms of turnout. I wouldn't pay good money for polls in this election - they're going to be even less reliable than usual.
Tend to agree - doesn't mean that polls aren't useful in determining with very broad brushstrokes the way the electorate is swinging. The margins are decided on turnout and how correct pollsters' assumptions are as you say. It's perhaps best to use them as a guide rather than anything more. Still useful imho