Repeat entries but starting from offset
You can't do this with the criteria parameters offset and limit. I would suggest to first get all the IDs of your section and then use Twig's handy cycle function to get those entry IDs you're interested in.

That function starts to read an array from the beginning again, when it reaches it end, so that's exacly what you need here. So when you want to get the 8th element of an array of length 7, it returns the first element (monday)!

The first element / ID of your array is in position 0, so I sustracted 1 from the week day number before passing it to the cycle function.

{% set allIds = craft.entries.section('schedule').ids() %}
{% set nextIds = [] %}

{% set start = now|date('w') - 1 %}
{% set end = start + 2 %}

{% for i in start..end %}
    {% set id = cycle(allIds, i) %}
    {% set nextIds = nextIds|merge([id]) %}
{% endfor %}

{% set entries = craft.entries.id(nextIds).fixedOrder(true) %}