Nazir 36: Combined Foods and Transferring Ritual Impurity

Nazir 35 discussed cases that include a generalization followed by detailed descriptions followed by another generalization. Today's daf looks at the reason the rabbis looked at that principle: what and how much food is forbidden to a nazirite.  

We understand that an olive bulk of food is considered to be 'significant'.  Priests eating ritually impure food is not allowed.  If an olive-bulk of forbidden food is eaten over a long period of time - the same time it takes to eat a half-loaf of bread - a priest could be liable to receive lashes.  We learn that a half-loaf of bread is equal to either three or four egg-bulks in volume.  Further, we learn that the time taken to eat that much food might be anywhere from three to eight minutes.  Is this the same whether or not the impure food is combined with ritually pure food?

The rabbis walk through cases that do not clarify their thinking for me!  One regards a bowl of thick soup that contains mostly produce (which is ritually pure as it was given as teruma from first fruits).  The soup also contains garlic and oil which are not ritually pure.  If a nazirite who has become ritually impure and then immerses him/herself then touches the soup before sundown (when s/he becomes fully ritually pure), the entire soup is forbidden to a priest.   If the soup's main contents were ritually impure and it was touched by a not-quite-pure person, only the spot touched becomes impure.  

The measures of teruma (between one fortieth and one sixtieth of a person's harvest) seems strangely vague to me.  By Torah law, we learn that even one grain of first fruits can meet the requirement to give teruma. Why is this measurement so imprecise when so many others are painfully detailed?   And how would/do people determine the proportion of ingredients in a soup so precisely?

Another example of products that have mixed ingredients, some tamei and some tumah - is when spices fall into two different pots.  Yet another involves eating kutach, a dip made from mouldy dairy that is so strong tasting that it takes longer than most other foods to consume.  How do these circumstances change the time requirements mentioned earlier?

I know that much of today's daf was cloudy for me - I'm missing information about a number of different concepts and principles - everything from separating teruma to determining ritual impurity to transferring ritually impurity and understanding the specific restrictions on nazirites.