Junts won't vote for PSOE unless they give Catalonia a referendum, which would be demanded on Basque Country as well.
They may get them to abstain however, which would give them a frankengoverment, although I think Pedro is capable to steer such ship.
However I think second elections are more likely. Vox is going down and theres probably civil war in PP with Feijoo vs Ayuso. Unless they fuck up big time its all in PSOE favor.
Bildu has not asked for a referendum and won't, they will be supporting PSOE.
But Junts has said they would only support PSOE if they got a referendum on Catalonia. Giving a referendum to Catalonia but not Basque country is not going to sit well with them.
Saying that half of Bildu doesn't vote for independentism is crazy. There are probably some cases but really not widespread.