Is there an optimal configuration or any way in which I can effectively connect
Ok, I'll be that guy.

tl; dr version: want to go fast? Forget hopping-up your e-bike. Get trained and licensed for a motorcycle, then go get one, electric or otherwise. You will be happier and live longer.

Now, what will be your speed result if you add the batteries? If you overcook the bike's chassis / brakes and plant yourself into a tree... zero. Assuming you don't fry the controller first, as Brian Drummond commented.

What's the problem? That setup of yours with its passel of lead-acid batteries is heavy, and has lots of kinetic energy when moving at speed. Not a good combination for an e-bike to begin with, and by adding even more weight and more speed you're just making a bad situation even worse.

In all seriousness, if going fast in an off-road setting and not on multi-use trails is your goal, consider something that is built to do that, like the Sur-Ron electric dirt bike (also marketed by Segway.) More here: https://lunacycle.com/sur-ron-x-bike-black-edition/

Even better: https://www.ktm.com/us/e-ride/

Do not consider something like this, which is an accident waiting to happen (and an approximation of what you're intending to build): https://www.onyxmotorbikes.com/products/rcr-72v. California DMV is currently investigating these guys for violating the e-bike classification.

In general, e-bikes have proven themselves to be a hazard especially for older men, even when they obey their e-bike classification rules. Why? They encourage less-fit and less-skilled riders to use them, and ride them at higher speeds than they could without the e-assist. More about that here: https://www.theguardian.com/world/2018/apr/25/older-men-using-e-bikes-behind-rising-death-toll-among-dutch-cyclists