There is an NPC, Kingseeker Frampt, that will consume your items in exchange for souls. He appears near the Firelink Shrine after you have rung the two bells. So yes, there is a way to sell item, but not until later in the game.
However, there is almost no limit to the number of items you can have in your inventory (see this question Is there a limit to the number of item in inventory?). You can hold up to 1984 different items in your inventory, and if you purchase the Bottomless Box, from a merchant in the Depth, you can store all those items in it and have a manageable inventory.
However, I think you should just drop the duplicate items because the resell value is really low. This table, from one of the Dark Souls wiki, shows how many souls you'll gain from each class of item:
Weapons 50
Armor 100
Dung Pie 200
Cracked Red Eye Orb 500
Copper Coin 1000
Some unique items 5000
Even if you resell 1000 longswords, you'll only gain 50000 souls. Compared to the time it will take you to sell all of them, and to manage your inventory, I think it is not a good trade-off. There are quicker ways farm souls.
During your second play through, reselling some of the unique items may be a cheap way to get some souls. However, reselling basic items does not seem interesting to me.
You are correct that the Drake Sword does not scale with your stats, as many other weapons do.
With the sword upgraded to +1, you'll be doing 220 damage. Upgrading it to +5 will take this up to 300 - but at the cost of 40,000 souls and many dragon scales (9, I believe).
Having a +5 weapon that takes your stats into account, while it might give less "base" damage, would deal more damage overall because of your stats and so it should be considered.
However, you would lose the Fire and Magic resistance bonusses granted by the weapon. These are not likely to be significant, but you may notice firebombs and the like dealing more damage than they had before.
Best Answer
There is nothing special about these statues.
It's been quite a while since I've played through Dark Souls 1 and I can't test if there is anything special about the statue right now. It could also be an enemy that is simply just "hiding". From Software likes to do that sometimes, especially in Dark Souls 3 where there are some enemies that just hide somewhere and will not attack you when you get close to them. Some of which, you can't target, others you can.
If you want to check if it's a living enemy and not kill it instantly, punch it with your fist
There is also no entry on this statue on any wiki as far as I can tell so it's pretty safe to assume that there is nothing special about it.