A client queries; a copywriter responds: 

•  %, percentage or per cent? – I think the default should probably be ‘percent’ – all one word. Percent is US; per cent is British. 
• Fullstop after each bullet or not? – default is no. On the basic principle of minimising clutter (ie, anything that adds no value). The exception being when one or more of the bullets contains more than one sentence. In that case, the first sentence ends in a full stop, so the second can’t not have one; if one bullet has a full stop, all other bullets within that list (for consistency’s sake) also have to have full stops. I try to avoid multi-sentence bullets, not least for this reason.
• & or and – always the word spelt out, other than in contexts/phrases where the use of the & is well established – A&E, P&L, fruit & veg. You would never, eg, talk about ‘our recording & publishing businesses’.
• USD$ (then space) or US$ and no space after – I would say US$no space. USD$ = ‘US dollar dollar’. And as for the space, we wouldn’t say £ 100, and ‘US$’ is just their ‘£’, albeit a three-symbol rather than one symbol symbol. So, £100, US$100.