I don't bother sowing parsnips and carrots until the first week in May now. Always a better outcome than earlier sowings.
Yes I do that. I've covered a strip of the plot with 3 inches of compost & then put porous black plastic back over it. I won't look at it again until the end of April. Hopefully the weed seeds will all have germinated & died by then. I'll sow parsnips, carrots, Giant Red celery, a bit of dill and whatever other row crops I ran out of room for elsewhere(!

) directly into the compost layer.