FFS. Try understanding how margin requirements now are very different then 1929
Initial margin requirement For new purchases, the initial Regulation T margin requirement is 50% of the total purchase amount. So if you wanted to buy $10,000 of ABC stock on margin, you would first need to deposit $5,000 or have equity equal to $5,000 in your account.
Now for more experienced and larger portfolio's the margin requirement may be lowered to 25%
So for small accounts your position has to drop 50% before you get a margin call / forced sale .
Again ...in 1929 your position had to drop only 10% ...and it was automatically sold thus causing prices to cascade .
As I've stated before ... a retest of recent lows is a distinct probability . A repeat of 1929 or your view ...a full reverse of the 2009 to 2021 bull market ...is not going to happen