Your argument here ignores the fact that CO2 is a much more efficient green house gas than water vapor. CO2 accounts for apx 10% to 30% of the green house effect. Another issue is that water vapor is basically self regulating for a given temperature. ie: H2O in the troposphere is a feedback effect linked to temperature which is linked to the level of CO2, CH4, and O3 in the atmosphere.
So how come the scientific agencies and organizations who dont get there funding from specific special interest groups dont have numbers any where near what your saying? And even at 10 times the greenhouse effect number our .03 % is still only equivalent to a .3 % of total greenhouse effect. Thats still statistically below the valid minimum noise floor level. that would still mean the remaining 99.7% comes from naturally occurring sources.
Yes, the oceans are a huge CO2 sink. In fact, the CO2 absorption by the oceans is turning them acidic
World wide sea water PH is between 7.5 and 8.4. My chemistry books say thats slightly alkaline (basic) and documented geochemistry tests and studies suggest it has been that way for a many millions of years now with only slight variations during the peaks and lows associated with the global ice ages.
For reference your sweat has a PH around 4.5 - 5 which is acidic. Typical potable water can be any where from 5.5 - 8.5 PH depending upon the compounds it contains.
CO2 levels in sea water are stable simply because so much of the plant bio mass is based there. They automatically take as much CO2 out of the water as is made available. This is a documented scientific fact as well and can be tested and proven in a high school level bio lab class.
Right now the ocean based biomass capable of converting CO2 in the water has a working capacity to handle the human annual output in about
three weeks time.
Also it has been shown the ocean based plant life has one of the highest reaction times to favorable conditions. Add a little of anything that it needs to grow and it explodes in growth until it has rebalanced its environment.
Algae blooms are a good example of how minute variations in a favorable source of nutriant material or compounds can generate a massive growth spurts in very short time frames of even as little as a few days! They absorb as much of the added nutrient as is possible then die off and sink to the bottom locking it away.
If your wondering, I am pulling this basic data off of rather general Google searches that bring up sites that have not been found to be liars and number fudgers!
The real scientific truth is really that easy to find. So easy even I can do it!