Right, MC's acted like that because he's actually suuuuper shy. MC behaviour towards ML is not okay but what can we do, he's a bbg at heart and in love with ML, but too scared to confess because MC afraid of getting rejected and their long-standing relationship turned sour.
Plus current Woojin is currently possessed by a ghost according to a plot stated on ridi(so not really a spoiler), so his personality turned 180 degrees because he's literally not the OG Woojin.
This is similar to all that Amnesia manhwa's plot where the sweet and possessive ML turned shitty after an accident, only difference was that it was not from a head trauma, but supernatural phenomenon.

Ppl saying the mc deserve it when you know u prob do the same too. Mc know he has no chance with the ml and realized that out of 90% chance the ml might not feel the same. To let those feelings go he distanced himself. Of course it's gonna hurt the ml but the mc is literally just protecting himself from getting hurt and there nothing wrong with that.