From what i understand Stalin had his own designs for western Europe, it just happens that Hitler had a bit less patience. Stalin was undoubtedly was a sly one just like Franco of Spain but Hitler's mien Kampf basically prophesied the plunder and rape of eastern lands explicitly the Slavic people, Hitler's intentions were known but not heeded at any point. Hitler played an excellent game of lulling his opponents into awkward positions and keep them guessing until it's was to late and he was as entrusted the Fuhrer - Hitler was adept at manipulating politically although war strategdy was a slightly different prospect.

Finishing off the British though in the Mediterranean I believe would place german in a worse position for the manpower as, to achieve victory in that theater the Germans would have needed to pump more troops into that arena. Eliminating the British nuisance at the roots could be achieved with much less effort (Britain is an Island thus once supplies are cut off the entire system will be distraught and desperate for an armistice with Germany) Taking Britain would negate extra troops being sent to north africa and Mediterranean and provide a wall for the britons to resist in any capacity. Strategically England was in a much worse position that the Germans who constantly worried about another two front war. The U-boats was exacting a horrifying loss to Allied shipping and if the trend continued all possibilities for the British to wage war would be removed.