Do not worry too much about a little smoke leaking from the cooking chamber door seals. Unless there is a big gap which is enough to prevent a good stream of hot air/smoke coming out of the flue then this will not noticeably affect the cooking or the flavour. If you see smoke billowing out through the cooking chamber door seal then add some stove tape but if it is the odd puff or small leak then you do not need to worry. Sealing around the door and lid in the fire box is more important so that you can control the air flow hitting the coals.
The meat dryness will be different...
Firstly, were you relying on the lid thermometer to measure your temperature? If so then it is likely that you will have been cooking at a higher temperature than you thought. It is always a good idea to invest in a dual probe digital thermometer that will allow you to measure the temperature at the cooking grate where the meat is.
The smaller offset smokers create quite a temperature gradient along the cooking chamber due to the relative close proximity of the food to the fire box. It is therefore important to rotate your meat periodically to ensure that it cooks evenly. The ribs closest to the firebox were probably cooking significantly hotter than the ones at the furthest end - and certainly hotter than the temperature gauge was telling you.
It is always a good idea to foil for part of the cook time until you are very comfortable with the temperature profiles of your smoker. Steve mentioned above that the 3:2:1 method is good for meaty ribs. This will keep them juicy and give you fall-off-the-bone texture. If you like them a little firmer then you can adjust this to 2:2:1
The brisket is more challenging than the ribs and it is easy to dry out. This does need rotating regularly in an offset smoker or one side will cook faster than the other. A good method for brisket is to smoke unwrapped for the first 3 hours and then foil for the remaining time. Most of the smoke flavour will have been picked up in the first 3 hours. Continue to cook foiled until it reaches temperature but then it is then important to wrap it in several layers of foil and leave it wrapped in towels (and preferably inside an insulated box) for an hour or so to let it continue to cook in its own heat.
The important thing is to get to know the temperature management and heat profile of your own smoker. Once you have mastered that you will be able to adjust the different techniques that you read about on here to suit your specific smoker.
Dont forget to post photos... We love photos
