What about fish being spawned on the land?
Was said to be fixed in 1.35 but I don't know if it works.
The heavy armors are useless
I havn't used them so I didn't pay that much attention, but I had several Obsidian sets before even one set of ebony armor was complete. What new heavy armors are there actually besides those you mentioned? You are right on the dread armor, its stats were pretty useless, especially for a high level character.
The Ayleid weapons, I found them rather too good for how easy they are to aquire. They are not only in dungeons with spectral warriors. I know at least three from the top of my head that a lvl 1 can easily pick up (not even counting those in the fighters guilt) and they absolutly wreck anything "suitable" for a low level. And I like that they are not the best weapons in the long run, otherwise regular loot might become pretty useless after you know where they are.
I like that most things are still somehow leveled. It would svck if you could get stuff much above your level from some random guy standing in front of a dungeon. That would really be too easy. The reward in OOO comes from the hand placed loot, not from leveled stuff and there is plenty of it imo. Regular guys are supposed to only give you standard stuff nearly all the time. By the way, once I got a strong Ayleid mace from a minotaur in the wilderness that a guard killed for me, that was just half an hour after I had started that character. Seemed too easy to me, too, but you should like it. Maybe some day your are lucky, too.
In the beginning, yes, most enemies are stronger than you, but it's always possible to take on stronger things if you are careful enough, try a few times and have a bit of luck. I have cleared sideways cave already twice completely early on with a low level character, with its multiple gargoyles and mystical imps at the end. You could try modding weapon damage to be more realistic. I use *2.5 for melee and additional *2.5 for ranged via Duke Patricks Combat Archery. OOO only increased damage by 35%. I also increased creature damage, but that only applies to leveled creatures, so I have much better chances against creatures early on. OOO is a very good basis for a mod setup, but it's not perfect on its own, try some other mods that help you with any issues you still have.
Default OOO leveling is very slow, best use another leveling mod, chose one of the faster options (also depends heavily on how much other quest mods you are using) or set your own prefered leveling rates, for example via http://tes.nexusmods.com/downloads/file.php?id=41005.
(like the full use of the Mage's Altar, which doesn't occur until level 37 in 000
I don't get that one. What happens at level 37?
For the uninstall, depends on how you installed it. I have it as an omod so just need to deactivate in Oblivion mod manager. If you installed manually, you will need to look what OOO added in your donwload and delete these files manually from your data folder.