Prepositions before and after percentages

Most of the time I do use a preposition after a percentage. Here's how I would word the examples you gave:

Further, 73.83% of the time the word "bloody" is said...

...while only 26.16% of cases

...75.6% of the time...

I would phrase this as follows: Further, in 73.83% of cases, the word bloody is said, while only 26.16% of these cases... We can see that in 75.6% of cases...

Note that whether or not the is used doesn't depend on the % symbol. It depends on the sentence, and the is used as per the normal rules.

There's a piece of land we own. 90% of the land (we're talking about) is cultivated. [The has to be used]

65% of children play computer games. [Not the children, unless it is specified which children are we talking about].

Examples are from oxford

So to know whether or not the is needed, we'll require your whole sentences with context.

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Same goes for in. It is included/omitted as per the normal rules.

Compare:

• In is required
  • In most of the cases, we succeeded
  • In 70% of the cases, we succeeded
• In is not required
  • We can notice that most of the times...
  • We can notice that 20% of the times....

Don't let the mathematical symbols confuse you. As a matter of fact, you should always write fifty percent instead of 50% .