india ink over minwax stain  

Ideally, you would use india ink
on freshly sanded bare wood, seal it with shellac and then varnish on top of that.
Idia ink is a very good stain for "ebonizing" wood, but it is essentially a water-based stain and applying it over an oil-based product could result in film compatibility issues. It's not what you want to hear, but I'd advise removing the oil-based product before using india ink.
You didn't mention species of wood or total area. Either could pose additional challenges. If you do end up using the ink, be sure it's labelled "permanent" and is a good artist's grade.

India ink
Is water plus soot (carbon) plus a water based hardened or adhesive. So if you put that over a coat of oil based stain, you best case scenario would be a died film that peels.right off the top, leaving you right where you were. You worst case is that the oil based stain has not completely saturated the wood's ability to absorb, and some India in does soak in leaving the surface even more splotchy than before, and with a film on the surface that will peel off immediately.
The only thing you can do now to even out the "color" is to apply oil based substances or sand it and start over with water based.
So you could apply more stain. You could darken the stain with black oil paint. Basically the stain is just thinned paint anyway. It is applying an opaque black film on the wood, covering the wood. Due to differences in the wood it is very hard to get just the right amount of this on there so that the grain shows through, and the floor doesn't appear splotchy.
The better way to ebonize a wood, especially if you want an even tone, would be to sand the oil off, apply a quebracho bark powder tea to the surface to increase and regularize the tannin levels across the floor, and then apply iron acetate (vinegar that has eaten some steel wool) or iron sulfate (available in nurseries to correct leaf yellow iron deficiency). This causes a chemical transformation in the tannins that makes them black, but leaves all the character of the wood because the color is in the wood instead of on top of it. There are much better tutorials for this process if you google something like "ebonize wood iron"

Can't the wax be removed with terpentine
or another comparable product, wich dilutes oil
or wax?

Minwax brand
oil based stains are not a wax (non hardening), but rather an oil based hardening finish designed to go down underneath subsequent layers of clear coat.
You'd need methylene chloride to strip it. Or sand paper.

what about mixing poly with stain
Ok I think I understand that I shouldn't use india ink. I will forget about that.
What about if I mix 1:4 ratio of same minwax stain and oil based poly and do one coat...especially in areas that are lighter, then apply coat of oil based poly by itself on top.
Would that work?
Also before doing that I was thinking of using a rag damped with mineral spirits to lightly remove a little stain in one area that is specifically way darker than the rest...
Does anyone think that process would turn out ok?

Mina, it would help if you tell us
the effect you're trying to achieve and the type of wood you have.
Really, there are countless options and words can only go so far without some reference.
Do you want your floor to be solid black, or do you want the grain and warm tones to show through a semi-transparent glaze type of finish? Can you find a picture on the web to help illustrate what you're after? Perhaps you could post a pic of what you've done so far?

Tktoo is right
To be of more help we need more information.
Regarding the idea of mixing some poly and minwax stain: I would coat a scrap piece of wood (same species as the floor preferably) with the stain and then try coat it with your custom mix. Theoretically since they are both oil based they will do what you expect, but....
What you are currently doing is basically painting your floor with oil based paint thinned to some degree of opacity (not something I would do, but to each his own), so if you use an understanding of how oil based paint/finish works you may be able to figure out how to plot a course that gets you where you want to go. Alternatively, it might not be possible to there from where you are without going backwards (an india ink or an iron and tannin ebonization for example).

not necessarily black just a...
not necessarily black just a dark brown, but now most importantly we want it to be even colored and not blotchy like it is now. So now we we thinking of doing the process I stated of mixing the stain with poly to even the lighter areas and then with a damp rag in mineral spirits rub off some of the darker spots and then finish with 2 coats of poly without any stain mixed in.