Align MTR and cliff computations

Currently we compute MTRs with a delta of $1,000 (hard-coded), and compute cliffs with a delta of $2,000 (parameterized). The adult parameters are also both set to 1. Can we align these to use the same parameters?

Locate the MTR and cliff computation entry points, then compare their delta handling and adult parameters. Confirm how the existing hard-coded and parameterized values are used; the work is done when both computations use the same parameters consistently and the relevant checks still pass.

Written by the indexing model from the issue text.