Consider this dataset which includes information about passengers of the Titanic.

Create a Jupyter notebook file that contains the following:

1. Python code to clean the data, remove any missing values, then find the mean, median, mode, standard deviation, and variance of each numerical column in the dataset.
2. As the dataset doesnt contain the weight of adult passengers who were on the ship, and given the fact that the average weight of adults between ages 20 and 50 is 90kg (with a 50kg variance), write Python code to generate a number of weights equal to the number of records in the dataset using normal distribution that simulates the actual population.
3. Find the probability of having someone of a weight less than 50kg.
4. Find the probability of having someone of a weight between 100kg and 120kg.
5. Find the probability of having someone of a weight thats exactly 77.7kg.