- Is an electoral coalition (to get the extra 50 seats) a legal possibility?

There are some requirements (the coalition should run as a united list), but yes. It is.

If yes, is it a political possibility in any constellation? You repeatedly wrote about KKE's going-it-alone attitude, but what is the relationship of SYRIZA and DemAr?

Apparently not. Only SYRIZA is pushing the idea on the left anti-troika side of the table, but the others are not budging. The CP condemns the opportunists who are trying to "save capitalism". The Democratic Left, is trying to be very posh and serious and are flirting with a position "memorandum bad but now it is a done deal, and let's accept it and move forward" so they are not responding either. They are accusing SYRIZA of being some sort of extremists, while they are the "responsible left". Despite the fact that SYRIZA's Left Front platform (demand a moratorium on debt payments for 3-5 years and use a fraction of the money to heat the frozen economy, in some sort of stable environment) is a bit to the right of Paul Krugman.

The Greens seem to be in a bind as not all of the polls show them over the 3% limit. They're vacillating.

Can DemAr be trusted to not fold to the troika once in government?

IMHO, no. They'll lose a few MPs if they do fold, but their right wing is openly pro-troika already to some extent. If they do score as well as the polls show, it is certain that much of their parliamentary team will be former PASOK MPs and cadres...

how do you estimate the chances of Anexartiti Ellines? (Will it be a bursting bubble or could it further damage ND?)

It will damage ND. They have the conservative unions with them, mostly, and quite a few populist commentators and journalists. They have the ear of the conservative grass-roots.

The road of excess leads to the palace of wisdom - William Blake