Increasing blood flow isn't the kind of thing that is going to make a huge difference (pun intended!). You may get more growth or it may just get larger when erect. So definitely YMMV. It's something that is not so much an exact science. Several of the surgeons who do lower surgery (metas) recommend it. Another reason is that it can stretch the skin. Be super careful, these are the family jewels and you can injure them.
Stop if it hurts and kind of take it easy anyway. It should NOT hurt, if it does you are going to fast and too much pressure. I think it can feel a little odd but that much is normal.
Yes, I think it can help dysphoria. You feel your little phallus very much so that's my impression of how it could help dysphoria.
--Jay