Heh, good story, you can tell it to your grandchildren, if you stay on long enough to have any in 4D.
My condolences - you seem to have had more than your fair share of bad luck.
I'm particularly shocked by your encounter with an aggressive biting jellyfish. Not so much by the biting, since 4D is known to have snakes with arms and legs, but by the fact that is showed up in a low level zone like the Serf Village.
It had no business being on dry land at all, let alone being in the Medieval Dimension, since it belongs to the oceans in Prehistoric...
The only explanation I can think of is that one of our oldbies must have been fishing in the river Maine, caught the jellyfish by mistake, and failed to follow the general rule of fishing; "Kill what you catch".
I take it you never got to poor Hanna, which might have been just as well, The Serf Village may be a newbie zone, but helping her with her baby is not a newbie task, since it involves finding the father of her illegitimate child, who is one of King Arthur's gallant knights, and resides in Camelot, in the other end of the Medieval realms. And there are many dangers along the road to Camelot...
This is one of the drawbacks of having a seamless world - there is no obvious warning when you leave the newbie area to enter something more perilous.
A tip is to stay on the roads, they are relatively safe as long as you don't attack anything. Venture off the roads and you might land in all kinds of trouble.
Another tip is to consider everything before attacking, that should give you a clue about your chances to survive the battle.
A third tip is of course to set your wimpy pretty high. "He who fights and runs away, lives to fight another day".
A fourth tip is the command WHERE, which will give you the name of the zone you are in. Combined with the command HELP <DIMENSION>, this can give you the levels of that zone, without having to run back to the Map Room all south of Recall.
Apart from that, the Map Room is one of the best tips I can give, because it not only gives the size and levels of the zones, but also a short background story, and usually some directions about how to get there.
Hopefully you haven't got too discouraged by your adventures.