Respectfully, there is a lot of misinformation in this thread.
There is no indication for warfarin where plavix or prasugrel are alternatives to treatment. And the reverse is also true. There is no role for warfarin in someone who just recieved cardiac stents (at least not for the stents themselves, the person may have another indication for warfarin though).
Plavix and prasugrel inhibit platelets and are used after cardiac stent placement (or even stents placed peripherally) and also for other problems caused by significant atherosclerosis/narrowing of blood vessels throughout the body.
Warfarin is an anticoagulant and does nothing to platelet function. Antiplatelet medications do not confer thromboembolism risk reduction in the setting of mechanical prosthetic valves, particularly not a prosthetic mitral valve, which has the highest risk for thromboembolism hence the higher INR goal range compared to a prosthetic aortic valve, for example. To my knowledge, a trial of antiplatelet meds for thromboembolism risk reduction has never even been attempted with a mechanical mitral valve and the various trials done on valves in the aortic position, which has lower risk, have all failed. Please do not try to trade from warfarin to plavix. Your doc wont let you anyway and it would be wildly foolish to do on your own.
This is not to say that there are not people on both warfarin and an antiplatelet medication (like plavix) but the indications for each drug are different and again, not interchangeable.
Warfarin can be a bitch because it interacts with many many drugs and this can either raise or lower the INR. The first step is to make sure your dietary intake of vit K is not variable. It does not have to be low, just don't let it be all over the place. You can have leafy greens every day, just make sure you have them nearly every day. This would likely result in you needing a higher dose of warfarin but the end result might be a less labile INR.
Since you're running gear/various compounds you should see if your doc will approve you for a home INR machine. There's at least one on the market and this would allow you to check your INR at home weekly instead of just once a month or whatever at the clinic. Also, if you introduce a new compound you can test yourself after a few days to see what's up with your INR.
Neither vit K nor leafy greens are contraindicated in someone taking warfarin. You just need to be consistent. Again, your warfarin dose might need to be a little higher if you eat greens every day, or even take a daily vit K supplement, but the INR is still the INR. Changes like that to your diet/ supplementation should be done under close supervision but as i mentioned above, the end result might be a less labile INR as the vit K level in your diet would now be much less variable. Too many healthy foods have vit K so it is not worth it to avoid them altogether, IMO.
Also, vit K is the appropriate "reversal" agent to be given in the setting of a markedly supratherapeutic INR. If you were actually bleeding they would have given you plasma in addition to the vit K.
I am surpised you listed anadrol as a compound that did not raise your INR. Due to the strain on the liver, oral AAS would be more likely to raise your INR than injectable ones.
Sorry for the long-ass post. See if you can get a home INR machine. You need to establish yourself as a capable patient and the incidents with you having the high INRs might actually help your case, making the argument that you'd benefit from closer monitoring and could be trusted to do it weekly.