Re: Body measurements vs ease
If you have a garment in a similar style, fabric type and weight, of which that you like the fit, I always find that measuring that garment's pieces, and comparing them with the pattern pieces (not forgetting about the extra on the pattern for the seam allowance!) is reassuring.
If still not sure, make up the garment in an old(charity shop?) sheet first - if the pattern's for a woven - just the main pattern pieces, stitched up the seam lines with a fairly large stitch so it's easy to unpick, no collars or trimming or facings. Set on one sleeve only unless you are very asymmetrical. You or more likely a helper can simply duct-tape the back seam - or any other where there should be a zip - closed, edge to edge.
Now you've just made a toile - and you can make and mark all your fitting alterations on it much more easily and effectively than on a tissue pattern or the lovely fabric you've bought.