You have explained every point in great details and you have published a very high quality post.

To solve this issue,SegWit advocated increasing the block size from 1MB to 4MB without changing the older version.

That's correct . It was done by removal of signature of witnesses from block data so that only transaction data can be stored in a block and as a result mm ore transaction data can be stored within a same block and within same block generation time more transactions could be verified.

Excellent efforts . Good luck .