I don't understand if the capex reserves should be excluded from these types of calculations, or if it should be included somehow?

This allows homeowners to exclude up to $250,000 ($500,000 for married couples filing jointly) of capital gains on the sale of their primary residence.

When calculating your freedom number do you include the mortgage, taxes, and insurance on your rental(s), or do you exclude that since those expenses should be covered by the rents?

The following categories of individuals and entities are excluded from the act and this chapter:(1) An owner of real estate with respect to property owned or leased by the owner.

If they don't pay within the three days excluding weekends and holidays, then the attorney can begin the eviction.

If the parcel with the home is on county records are "commercial vacant land" you may be able to get an appraisal (assuming enough value in the 4-plex) which excludes the home.  

Before you've owned it long enough to appear on tax returns, an investor friendly lender will just do [ rent * 75% - PITI ].Once it appears on tax returns, if you need/want to exclude the one-time rehab expenses, put it on line 19 of schedule e with the comment "see statement X," and then statement X in extreme detail lists all the repair and rehab work you did, and furthermore you can provide me with every single receipt/invoice, exactly matching the line 19 number, exactly down to the penny (so, it's best just to make each invoice/receipt be a line-item on statement X... if Contractor John gives you 5 invoices throughout the project, show me 5 line-items).Only one-time repairs/rehab can be discounted from the mortgage DTI math.

Is there enough value in the land itself that a loan can be made just on the land and exclude the mobile home entirely?

Most animal or vermin damage is excluded under most policies. 

In that case the payment could be excluded from DTI calculations.