May I ask why it has been a long time since you have played Late Surrender? Can you please tell me what you have been playing instead?
No surrender, ES and ES10 games. I haven't played late surrender games because the places I played didn't offer them, for the most part.
You have to memorize all those values?
No you do not have to memorize EV charts.

That is what you mean by Index Numbers?
Yes.
Is it no longer true that only Atlantic City casinos offer early surrender?
Yes. To my knowledge full early surrender is only offered in South America, although I am not widely traveled so you may find it elsewhere.
If not can you tell me whether Early Surrender is an important part of a winning strategy?
Early surrender is a favourable rule but you can still win without it. Rules are not really part of a winning strategy, they are simply conditions to which you must adapt.
How about Late Surrender? How important is that I use that?
If it is available you use it. Surrender in any form is very beneficial to a card counter because it is a higher ev play with lower variance.
One question about this web page. It gives rules for one, two, four, six and eight decks. But what about three, five or seven decks.
Odd number deck games are extremely rare, I wouldn't worry about it. Anyway you can use the same indexes for all multideck games.