I've been seeing this girl since November. She's 20, not very experienced. I don't know how a PUA would rate her looks, but for me she's about a 6-7 in the face, 7-8 in the body. Japanese guys won't touch her because they want cutesy body-like-a-plank submissive girls that will stay at home and cook, not athletic plus a couple of kilos (god I love her ass and hourglass waistline) of curves with a tomboy independent attitude. She works multiple jobs and doesn't have much free time so contact between dates can be a little sparse and setting a definitive date is nearly impossible now because she never knows when her off days will be (part-time shift work is fucked up in Japan). Basically she will text me when she's free and if I'm free we'll go out. Between then we'll bounce date ideas off of each other or send a funny pic. At any rate, seeing each other once or twice a month seems to be the norm for working people here.

We get along super well and always have a ton of fun together. She's a fickle person and gets tired of things easily, so if we didn't have this much fun together she would have left long ago. She's a bit perverted and likes sex but is so shy about it that her attitude/body language when she's DTF isn't any different than when she's having fun but not DTF. I never find out until I start escalating while making out with her, and the thing I don't like about that is that I don't want to come off as only wanting sex, but at the same time I need to consistently fuck her good so she has twice the incentive to come back. When we're alone and in high-spirits we get into tickle/wrestling fights and that's when I go in for the makeout. If she's receptive she will let me in. If not she will tell me to stop, hit me a few times if I don't, and if I don't stop by then she will call me "persistent" in a bad way. The word has a very negative connotation here. I've missed two chances recently. The first time she was still on her period and I'm not a fan of period sex. Tried it, not my thing. We also haven't discussed that boundary. The second time I had a prickly five o'clock shadow and when I kissed her she said it hurt too much. The last time I had facial hair issues I shaved but by the time I was done she was no longer DTF.

I want her to keep coming back for more, but I don't know how to balance always wanting sex and not giving her enough of it when I can't tell when the hell she's actually in the mood for it.

From a "pua" perspective, I know you're exclusive but she knows you don't have options other than her hence the brushbacks. If this girl is only seeing you 2x/month I'd expect she'd want to be ripping off your clothes when you're alone with her, not rebuffing you because of some stubble. You only see her two times a month and on those times she is giving you the cold shoulder from time to time? Find another girl is my suggestion.

It looks like I need to clear up some details. These responses are evidently from a breakdown in communication on my part.
She doesn't know whether I have other options than her, and likewise I don't know if she has other options than me. It's possible although highly unlikely. We've never had that discussion. However, from the second date she told me how she was looking for dating long term (i.e. 5 years or so) to marriage. So a slight departure from PUA stuff there. Now that said, I have seen two girls in the mean time but not gotten along with them as well.
Incorrect. She is the one who initiates the wrestling. This is her way of asking--or so it appears. When she initiates the wrestling, I go for the makeout, escalate to sex. The first time I was rejected she didn't initiate physical shenanigans, so I just misjudged that one. The second time she initiated shenanigans but she was on her period and thus I didn't move in. The most recent time we met and didn't bang, it was just a shitty situation because we got stuck in an internet cafe with no privacy. She had work the next day anyway. Also stubble. Out of the 6 girls I've dated/hooked up with (yeah I know that's not a lot) not a single one hasn't bitched about or gone cold on me because my stubble.

I'm starting to think some issue are cultural, some issues are her lack of experience (it seems like she's quick to settle into "I have my catch so I don't have to work for it" mode), and just being busy working multiple jobs. Barely a year out on her own and $800/mo. rent doesn't pay itself.

In my view she senses you don't have other options, and overall she doesn't seem that into it sexually. Try not to take it personally that she isn't dtf a lot of the time; just meet a girl who is.