Ok you are not at all getting the statistics of this. The chance is 18% that the stock would end in 3 months below 175. There is a 36% chance that the 175$ will be touched based on statistical analysis. These are elements to take into account when setting up a trade like you have. A 20% drop - certainly for a stock like NVDA - is not at all out of the question this can happen and its not a black swan event.
So taking your statement that you will bail +- two thirds of the way in, this means you could do a trade like this (with modified strikes if appropriate) 6 times a year as you are in the market for 2 months for each trade. Based on the current prices you might exit for as little as 0.20$ net cost every time you are successful and lets presume you are successful 5 times out of 6 so that would net you $10,900 however we must also presume that the one failure will materialise.
For the sake of argument lets say NVDA would drop to 160$ - halfway to your lower bound. Presuming you bail out at 1 month before the end then you would lose ca. $12,700 (likely value of the spread is $15,000 to buy back minus $2300 credit received). This means that after a whole year of doing this you are coming out with a loss of $1900. Now to be fair these calculations are just the ones I did in my head and they should be made more exactly for example to allow for the fact its a 2 months not three months trade. However, your statement that
is based on 1/5 chance. Make less sense than 4/5 chance it will stay above 175 strike.
Is the one that doesnt make sense, the statistics shouldnt give you a false sense of security. If you showed me 5 doors and told me to walk through one of them. 4 doors give a million dollars and one of the doors leading to certain death; you wouldnt get me to go through any of them. The challenge with all such spreads is how to avoid taking the one big loser - all I was saying was that your setup seemed decent. That as long as you could manage the downside risk and position size it was a valid position. The 18% chance that it goes wrong shouldnt be underrated though - this is a very real percentage and the losers in credit spreads tend to be much bigger than the winners.