Spain: Does anybody know what to do?

We have had an interesting week in terms of political developments. Finally there was a new attempt at investiture... and it failed. The presidential candidate, Mariano Rajoy, of the Partido Popular (PP), lost in the Congress of Deputies, in two rounds of voting in the last week, 180 votes against, and 170 votes in favour. This week began with an announcement of the other presidential candidate, Pedro Sanchez, from Partido Socialista (PSOE), although he said it would open the round of negotiations without being there himself, as he has presidential aspirations. Recall that this is the same Sánchez who was presented to the presidential investiture in March 2016 and he failed then too. Both failures note again, that it is easier to agree on what they do not want, instead of what they want.
In this scenario, the third elections are most likely an election that would match those of December 25th, if not avoid a change in the electoral law agreed by absolute majority, to reduce the electoral campaign to one week and then the election would be on December 18.
But let's talk about politics. What can happen in this scenario? Apparently anything is possible if there are agreements. The point is that there are no agreements, and I bet that there will not be until after September 25th because there are the regional elections in Galicia and the Basque Country, in which none of the major parties in Congress wants to make a pact and this will affect their results in both regions. Recall that the end of October is the deadline to form a government, before moving on to the third elections.
The blocks of possible agreements can be (questions included because more seats would lack to reach the absolute majority of 176 seats in Congress):
PP + Ciudadanos (Cs) + Coalición Canaria (CC) = 170 + ?
PSOE + Unidos-Podemos (U-P) = 156 + ?
With these sums as a starting point, the PP would need support of six more seats. But it would be complicated, because the only force with which a priori could agree is with the Partido Nacionalista Vasco (PNV), but it only has 5 seats, and again, remember the Basque regional elections on September 25th.
With the other minority parties with which it might agree, and considering those have 6 or more than 6 seats -in principle- would be discarded by being parties of separatist nationalism in Catalonia. Neither Democratic Convergencia Democrática de Cataluña (CDC) with 8 seats, nor Esquerra Republicana de Catalunya (ERC) with 9 seats, seem likely to agree anything with a government led by the PP government, but who knows... If we consider that politicians are moved by interests of power and not by ideology, perhaps they can reach another agreement. Do not forget that the PP made a pact with the nationalist Convergencia y Unió (CiU) in the legislature from 1996 to 2000. But the situation is now different because since 2010 when the regional president, Artur Mas, launched the separatist initiative, the political situation seems to have become tense, and moreover is increasingly more tense.
As for the bloc headed by the PSOE: It needs 20 more seats, and it needs necessarily to agree with those two parties of Catalan nationalism mentioned earlier, i.e. CDC and ERC, which would have 17 seats more, and perhaps 5 more from PNV, it would get 178 seats and the absolute majority to form the most fragmented government of all governments that have been in Spain since the Constitution of 1978. As the largest party in the coalition (PSOE with 85 seats) it would even have half the coalition of investiture, or maybe it would be a coalition government with ministers of different parties? Also, some former presidents of the PSOE such as Felipe Gonzalez and Jose Luis Rodriguez Zapatero urged that Pedro Sánchez ask for the abstention of the PSOE and let the PP rule with Rajoy to come out once from the deadlock and have a government that starts legislating, and an opposition led by the PSOE.
In many European countries, it is common for the existence of a coalition government with ministers from different parties. In the Spanish Constitution of 1978 it has never occurred in the state government. It only happened that support for investiture was traded in exchange for concessions, usually with the Basque and Catalan nationalists in exchange for more regional powers and more funding from the state government to those regional governments.
What can we predict about it? In principle, it seems that the PP is easier to get the necessary support because only have to get 6 seats and not 20 as the PSOE. But with the situation compared between Congress, separatism in Catalonia promoted by CDC and ERC (among others) as well as the upcoming regional elections in Galicia and the Basque Country, all make clear it is that there will be no attempt more for investiture until October. For now, we will find more attempts pacts by the PP, but mainly by the PSOE, as its leader, Pedro Sanchez, has got worse rating for opposing any pact with the PP while not proposing a government different. Of course holidays in Spain paralyzes everything. Although it would say that not much is needed to urge the Spanish politicians take more holidays. There are not who pay each costly electoral process.
So, until after those elections of September 25th, we probably will not have any relevant news. Unless Pedro Sanchez finds some "linnet" who wants to head a government of the PSOE, making it necessary to have the support of Catalonian separatist parties (CDC and ERC) and the Basque nationalists (PNV and perhaps from the Basque separatists EH Bildu). Another possibility would be that the PP seeks another possible presidential candidate who better is understood with the PSOE and so got -at least- the abstention of the PSOE, in a new attempt of investiture, and  a government will be formed during the month of October. Both scenarios seem unlikely, but since the general elections of December 2015, it seems that many unlikely scenarios are likely, as the breakdown of bipartisanship PP-PSOE, although this has led to a stalemate because Spanish politicians are not very used to negotiate with parties as large as they are.