Usually I recommend the WBS 6-12 months after initial treatment, but it depends on cancer characteristics (size, extrathyroidal extensión, adenopaties, ...) In patients with very low risk tumors the WBS may not be neccesary.
To avoid levothyroxine discontinuation, I use to perform WBS with previous TSHrh
No, not routinely and only if total thyroidectomy (usually with ablation) has been performed. The Tg and US are sufficient in the majority of the cases.