Like you I crossed over from mountain biking to the road about 7 years ago so I hope these comments are of some help.
You don't say hew tall you are but going by the planks on the shed your saddle is way too low in relation to the bars; even an untrained amateur like me needs them level or the bars an inch or two below the saddle. The saddle angle looks right, just cupping the pelvic bones so as not to throw your weight forwards. You can pad the bar tape with the Specialized Body Geometry gel pad system, not cheap but very comfortable, or just use that thin spongey wrap sheet that's used for protecting stuff in the post, laid in a strip so as to fill the gap between the bar and the cable and create a wider platform. Your bars are old-style; compact bars are better for an amateur as there's less drop. Be sure to get the right width though. If you weigh 75 kgs (same as me) then pressures of 95 rear/90 front are about right, buy some decent cotton wall tyres like Veloflex Open Corsas and use latex inners for a superbly grippy smooth ride. Wear mitts with padded gel palms. Ditch all flappy clothing as it will annoy the hell out of you. The braking won't feel as good if you're used to discs but fit some softer compound pads, Swisstop green are excellent, and get them set up right and they will be adequate even braking from the hoods. The good news is that after a few rides the body does get accustomed to the different position although riding down on the drops takes a little longer. You will get a lot fitter as road cycling involves longer periods of sustained effort and you're not constantly stopping like you do off road.
