Hi! Love to see a picture of your quaker!
While most parrot species are cavity nesters , quakers actual build structures. A cavity Mimicked by a dark space , like under a blanket my still be appealing. But I have had a male , ( tho this is only one , and individuals vary in a species) and while he was highly hormonal he never fought out dark spaces . Neither do my girl quakers .
My green cheeks most definitely do !
In general I just don't let my birds go under blankets .
Regurge, it can also be a family, friends thing and nit just mate thing . It certainly a sign of love . I try to not make them feel rejected, like ok thanks let's do something else , like walk over and look out the window, redirect.
Because of his age this probably just practice behavior. Basically ignore and redirect. Don't make a big deal about it