Outlook does not support border-radius (see https://www.campaignmonitor.com/css/box-model/border-radius/).
Are you able to supply us with your VML?
looking through your code I can't find any VML - have you removed it? (Could be me being blind!)
Anyway, have you applied an inset to the background?
This works a little different to padding - instead of being t,r,b,l. This is l,t,r,b - set the valu you want in pixels and it will push the content within the VML to where you want. Will require some trial and error to get it right but hope it helps!