1. No, its still summer/winter. Events happen later as well as those are year bound unless you change that too.

2. Don't know why its 1400 but if you put it at 1150 and require gunpowder discovered you won't get the unit until gunpowder is discovered and it it at least 1150. If you just put 1150, it is available before gunpowder is discovered.

3. You need to unpack those files. Actually you can just change a name at will in the txt.bin file to make it appear differently. Note that any such changes to either file may result in other characters having your name as well randomly.

4. Yes it will speed up events and anything else that is year bound but keep turn bound things the same. i.e. aging still at 0.5