Yes, use the Form Chinese Nation decision. (you need to annex Manchu and it has to be after 1650 or something like that)
Other then that, no, not really.
I hear that decision is bugged and will instantly crash the game? Was that fixed?
I'm currently progressing in a WC attempt as France but I am leaving most of Europe while I Holy War elsewhere until I can get the Cabinet NI for the higher cost of taking land in Europe. Due to this I have a ton of distant overseas provinces which are not giving taxes or production. Would it make sense to move my capital to Judea or another place in Arabia/Africa/Middle East so that mainland France and Turkey are distant overseas instead? I assume that once I have a full land connection from my capital to Arabia that they will no longer count as overseas.
It would make more sense to move your capital to one of the many European provinces in Anatolia (use region mapmode), so neither France nor anything connected by land to your new capital is overseas.
That's why it's so nice that the Caribbean is part of the North America region: you can move your capital to New York, making mainland North America, mainland South America, and the Caribbean all not count as overseas.
Though in your case, can you really afford the stab cost of moving your capital? In my WC, stability drops are still scary, and it's ~1630 with 336 colleges (lots of stab cost reduction). I didn't manage to get rid of the overseas modifier until after I was already pushing into China; I personally just pummeled Scandinavia and the Hansa until I could string a chain of forced PUs around the northern side of the empire and down into Russia.
What calvary is used for? Infrantry have like 10 points and calvary just 3 etc. and calvary is more expensive. How I should use calvary (playing hasa)?
Cavalry is superior until the mid 1700s or so. Go to the military screen and look at the place you can change your preferred units. On the right, it lists fire/shock/morale modifiers for them. Infantry have things like 0.5 for most of the game, while cavalry have things like 3. As in, basically, an infantry unit's shock stat of say 6 gets multiplied by 0.5, while the cavalry's shock stats of say 3 gets multiplied by 3, making the cavalry 3 times better than the infantry in shock.
If you're playing Haasa, this is especially the case, since Muslim cavalry is so strong early and mid game.