Whether I am using the Kettle, Jumbo Joe, or one of the WSM(s), I like to wait until I have a clean burning fire before I add wood or food. It's usually up to temp or close to it by then. Once I see no smoke is coming out of the top vent I add my food and throw a cpl chunks of wood on the fire (thru the door on the WSM). I plan an hour from lighting the chimney starter to getting a clean burning fire but it usually only takes ~ 45 min or less. I do not wait to burn down the wood. I want the thin blue smoke. All the smoke I see I know I added as smoke wood.
Filling the water pan will help control temps a great deal. A lot of folks here use a clay saucer, sand, or other heat sink as an alternative to water. Water absorbs a lot of energy therefore more charcoal is used to heat water vs the cooker/food. Also, the food mass will absorb energy and will itself help control the temps until it starts coming up to temp. Larger chunks of meat more so than ribs, but ribs will somewhat absorb some heat while they're cold.
Another way to control temps is use less lit charcoal. The lit lighting your unlit is a slower process and you can react easier. Dumping an entire chimney of lit is only required for high heat cooks.
I like to cook ribs at 275*F but yes, start closing your vents as your temp starts increasing. Don't think it's going to stop right at 250* unless you anticipate the increase and close the vents so the cooker rises to your target temp. I recommend reducing the vents to nearly closed (1/4 open) when the cooker hits 200*F-ish. It if settles in anywhere between 260 and 285*F I'm happy. Don't chase temps too far.
Another tip: go easy on the smoke to avoid the "ashtray effect". One or two chunks for most cooks is plenty in my world. Wood is like a strong spice. Go easy.
Also, we've all been there. We all had to learn our cookers. You'll get there, too.