Icelandic is part of the Scandinavian system where black gambits his e-pawn for quick piece mobility.

I am not in favor of the whole 5...Bb4+ system as it assists white's development. For me, 5...Nf6 followed up 6...Bc5 taking a strangle hole on the centre dark squares. Also 6...Qe7 is a slight positional inaccuracy because it takes away from black' pressure on d3. Instead, I suggest 6...Bxd2 7. Nxd2 Nc6 8. Ngf3 Qd6 with a good game for black

Interesting... thank you, I'll go through it.

When white liquidates the DSB he creates a serious weakness on the dark squares. Furthermore, as it stand right now white's best piece in his DSB. So it is not advisable to trade it.

IMO best was retreating the Queen and avoiding Q exchanges. As a Q swap would take much vemon out of the game. Best is 8. ...Qe7 9. Be2 Nc6 developing as normal.

I'm sure you're right, but it seems to make useless all the main idea: force white into my lines. After this, I have o-o-o, directly threatening Bxc4 and Ne4.

10. Na3 is a poor move that hands black a count-blanc over the position. Instead, forgoing castling rights and defending d3 with 10.Kd2 would have had somewhat equality.

Again, probably right, but Kd2 puts white's K just in line with my R... it takes a lot of cool blood to play it...

Black's attack on d3 is so huge that it does not matter what white does. Though following general principles of chess with 11. 0-0-0 offers a hail Mary's chance of successful defense.

o-o-o was better. If Nxa2+, Kb1, and my N has to retreat, leaving the a column open for his R to act. Against o-o-o, I'd have played something like Ng4 instead... threatening f2.

?? I do not like this move at all. Because after 12. Ke3 Nd6 white has mostly solved his problems and can likely hold on for a draw. Instead, the dagger in the heart comes from 11...Bf5! hitting at d3 with everything you got and winning a pawn.

Right, elyhim... white has no way to defend d3, and after it falls, white's K is completely naked in the center. Anyway, this N is heading to c5, not d6...

The white king is perfectly safe on e3 and one can make the argument that is actively engaged in the fight

Nc5 now is not good as d4 is possible for white.

You do have something concrete a.k.a the attack on d3. Logical is to build on it with 13...Bf5 at least that is what I would have done

Who can resist to put another R on the center opened column?  

again 14...Bf5 is best

finally!