rummikub 20,000 IU per day , is not a normally accepted daily dose.
Some people in some situations might take that , but under medical supervision. You would probably have no problems - but it is quite a high dose. Hypercalcaemia would be the condition to watch out for. That is the condition that would arise if Vit D was becoming toxic for you.
The IOM ( institute of medicine ) in USA have said that 10,000 daily is the NOAL ( no adverse event level ).
Perhaps it would be better if you limited yourself to that, then measured your blood level, after 2 to 3 months, if it is then in the range120-140 you are more than likely having enough. It would not be a worry if your blood level even reached as high 200, as some outdoor workers do achieve that.
It is possible that Vit D will help with your mood, especially if you have low levels now. Sufficient Vitamin d will help in the regulation of serotonin levels. It is also thought that omega-3 , will help when the brain comes to use that serotonin , i.e that the seratonin that you do have will work better. Give it a chance to work, ie. keep your blood level constant for months. Sudden ups and downs is not good.
4000 IU daily is often considered sufficient , if you are starting with an acceptable blood level.If you are starting from a low level, then a top up dosing schedule is sometimes undertaken. That is when 20,000 IU is normally used, but not long term daily.
D3 form is better to use , rather than D2 form. Daily dosing is better than intermittant very high doses.
good luck
BTBH