A lot of these details you are asking for aren't publicly available. Some of the answers I provide will be based on anecdotal evidence.
Keep in mind: The score is not everything. The banks look at all the details in your credit report and the relationship you have with the bank to determine your creditworthiness. You can have a great score and still be denied for credit .
If I miss a $3,000 mortgage payment by a month, will I get a 0 for my 35% of on time payments?
It's not black and white like that. For example, if you have 100% on-time payments except for this one month that can change how it effects your score. But yes it will tank you score.
Is that the same as if I missed an $85 student loan payment by a month 10 years ago?
No, the 10 year old late payment does not effect your score at all at this point. FICO weighs recent late payments much heavier than later.
Or if I missed a $1.95 CC payment in high school that I still haven't paid?
The amount of the late payment wouldn't matter but the fact that it happened so long ago works to your favor. If you still haven't paid that $1.95, the account has probably been charged off at this point and that is a much bigger problem.
If I recently refinanced, so I still owe close to 100% of my current mortgage, is that a black mark against my 30% of how much I owe, or do they not look at the mortgage piece for "how much I owe"?
Installment credit utilization is calculated and effects your score but not as much as revolving credit. They know when your mortgage was opened and they don't expect you to have a low utilization ratio on a mortgage that was just opened.
What are items that are worth disputing off your credit reports, and what are effective ways to do this?
Anything negative you don't want on your report. Google around you will find plenty forums dedicated to credit repair.
How long does it take different negative items to get off your report by themselves?
Late payments: 7 years
Bankruptcies: 7 years for completed Chapter 13 bankruptcies and 10 years for Chapter 7 bankruptcies.
Foreclosures: 7 years
Collections: Generally, about 7 years, depending on the age of the debt being collected.
Public Record: Generally 7 years, although unpaid tax liens can remain indefinitely.
How badly (and for how long) do pulls + new credit hurt, as compared with the benefit of more credit leading to a lower utilization ratio? Is there a way to calculate this?
No. But it depends on your situation. If your maxed out on a few cards and you add a few new cards and keep zero balances that will certainly help your utilization ratio. My guess is the points gained by your lower utilization ratio will outweigh the loss of points with the new credit and pulls. However, if your maxed out, your probably not getting approved for new cards.
If your mortgage is by far your largest credit, dwarfing your CC credit, and your utilization is high (meaning, you aren't close to paying it off) does this impact your score in terms of credit card approvals?
No.
How often should you put a few dollars on a CC you don't use for regular spending in order to make it work in your favor in your credit score?
0. But I would put a little spend on every card once every 6 months so they don't close your cards down for inactivity.
What are good practices in terms of managing CLs, both in terms of credit score and in terms of being approved for more CCs from the same bank in the future? Is it detrimental to have a wide variation between CLs on different CCs, independent of utilization?
Don't close down a card from the same bank before shifting the credit line to an existing or new card. A popular way to get approved for cards is to offer to close and shift credit from one card in order to open up a new card. And no.
Most of the charts showing different levels seem to group the over 700 crowd together, pretty much. Maybe there is another little break at around 740. Once you are over 74x, how much benefit do you get by continuing to increase your score? Obviously, you shouldn't do anything to negatively impact your score, but are certain banks known to have target scores one should aim for for easier CC approval?
If you have a score above 760 it's safe to say you are in the top tier at every bank. 700 and 740 is a big difference. I'd say 740 is A, 760 A+