I agree. You are on the right track with "disproportional amount of NHCEs;" more specifically, you have to pass the effective availability test with respect to the 3% match. Essentially the group of employees to whom the 3% match is available has to satisfy the 410(b) ratio percentage test.
Does "discretionary match" mean I can give everyone a different rate of match as long as it passes testing? Or that the match formula that applies to the entire plan is at my discretion?
Any benefit, right or feature that is available only to NHCEs is automatically nondiscriminatory. Besides the ACP test (which would only be helped by the additional contributions for NHCEs) I can't think of any other issues.
402(f) notice is required to be provided for any eligible rollover distribution. RMD is not an eligible rollover distribution; therefore, no notice.
The content of the notice describes how you can roll over your distribution and continue to defer taxation on it. With an RMD you do not have the option to roll it over, so providing the notice would actually be misleading to the participant.