I am not sure what you mean by 10000iu for 3 months and then 2000iu a month. 10,000iu per day for 3 months would be okay but 2,000iu per day thereafter is not really enough. You would be okay with 5,000iu/day. Be aware that dosages depend upon your circumstances. Darker skin produces less Vitamin D than lighter skin for equal sun exposure and your location and sun exposure are all part of the equation. Also make sure that you use Vitamin D3 rather than Vitamin D2.
K2 can be helpful to the circulatory system, keeping calcium where it is meant to be rather than being deposited in the arteries. With the vitamin D which might raise blood calcium levels it would be helpful. I use Life extension Super K which has 2.7mg of mixed K complex. I take that 2 or 3 times/day.
Magnesium is okay at 400mg to 1200mg/day and I would say get at least 800mg/day but the type is important. Chelates are quite expensive and Mag citrates are fairly cheap. Magnesium Malate is pretty decent and quite well absorbed. You could get Magnesium carbonate, which I have just received, and do an acid/base reaction in a cup/mug. Use some warm/hot water and an acid such as ascorbic acid, malic acid or various other acids and get a Magnesium salt which should be well absorbed. ie Magnesium ascorbate, magnesium malate etc. Magnesium carbonate is fairly inexpensive but it does mean reacting it before use which is not ideal when out. Magnesium malate tablets/capsules are fairly inexpensive for use when you are out. Do not use too hot water if you use ascorbic acid! The version that I got which is very white reacts very quickly with Malic acid or ascorbic acid, considerably quicker than calcium carbonate which is really slow to get to react.
A multivitamin which I use is Life Extension 2 per day which is fairly comprehensive and contains decent amounts of B vitamins in a mix of forms. It's not too expensive either for a 2 month supply.
I did try Inositol myself but not for OCD/anxiety. It just made me very tired so I stopped using it. It's probably a good idea to start low and increase, noting the effect. If you feel tired/sleepy then you are probably taking too much.
There are some amino acids which can be calming such as Glycine which again I take but I have to be careful because it can make me tired/sleepy. I often take it with L-Aspartic Acid for it's stimulating effect to counter the calming nature of Glycine. I need Glycine along with cysteine/glutamine/methionine for Glutathione production which my body has a high demand for.
Toning your liver energy should help with OCD more than anything else. If you look at your right iris at about 4 o clock and look for shadowy rings that run around your iris, they look like ridges in the iris and the width and depth reveal how strong an effect they are having. They can affect energy flow in the liver which would have a big effect on something like OCD. There are various chinese herbs which can tone the liver energy such as Tu Si Zi. I have used that for 20+ years with good effect. Be aware that it can be a little bit constipating.
Something else which should tone your Liver very well is German Chamomile essential oil. You need to get a pure form which is guaranteed pure and without any contaminants as it is fairly expensive so could potentially be mixed with cheaper oils. Finding a good source is essential! I use NHR Organics for mine. You only need a small amount as it goes very far so a 5ml amount would be a good place to start. Getting a small dropper bottle of about 20-25ml and filling half full with some pure water, preferably distilled to help prevent it going off. Then add one drop of German Chamomile essential oil to the dropper bottle. Put the dropper lid on and shake vigorously, you are trying to break up the oil in the water and suspend it temporarily. Quickly add one drop of that mixture into a cup. If you add it to some current juice it shows up better so that you can see the oil. Note that after using this for a couple of weeks, 2 or 3 times daily, the oil content will decrease and you will need to top the bottle up with more water and add another drop of the German Chamomile. Keep it cold in the fridge to help prevent it going off but the oil should help prevent that to some degree. Using some alcohol in place of water would help prevent any bacterial growth. I did try using some lecithin with the German chamomile essential oil but I did not like not seeing the oil content when I added it to the cup. It's very difficult to judge the concentration with all the lecithin hiding it.
If you can get some alfalfa fluid extract or possibly tincture it would be helpful. Alfalfa is yin in nature and would help calm you. It does tend to moisten the colon and loosen up the bowel. The combination would help counter act the effect of the Tu Si Zi. The more you have the greater the effect. Alfalfa is a Liver yin tonic and when combined with German Chamomile essential oil it directs the toning effect to the liver. I have used this for many years and the nerve rings in my iris are now very wide and very shallow in depth showing that the German chamomile has had a dramatic effect. I used to use Alfalfa fluid extract along with the chamomile but it's yin nature is not very compatible with my energy problems so I no longer use it, instead I use German Chamomile alone but the effect on the nerve rings is less as a result.
I am not sure whether B12 would be helpful if you get a reasonable amount in your diet which is absorbed adequately.
I hope that proves of some benefit to you. It should help a lot, particularly toning your liver energy/Chi which would help more than anything else but would take much longer to accomplish. ie 12 months if using alfalfa/Chamomile combination.