I'm installing custom door jambs with pine and hanging some solid wood doors. i secured the jambs in place plumb with 16g finish nails. Are these strong enough or should I hammer in something stronger? If so, what type?

Guys I'm going through the process of replacing my very leaky/drafty doors with new ones and next would be the windows. After that, I'll be hiring somebody to do the air sealing in the home, then insulation and finally get a new HVAC system based on Manual J calculations, etc. I'm basically trying to do the right thing to make this 100 year old home in the north east comfortable but at the same time, not spend through the roof. The good thing is that most of the above are very old anyways - the central HVAC system is 20 years old, the doors much older and the windows a mix Can somebody take a look at these pictures? In the pic where you see the steel rails/tracks, I can very easily feel the cold air coming in. The other type of window has a plastic covering but you still feel cold air. Are quality 2-pane windows constructed in a different manner that you would not feel any draft from the sides? Also, instead of replacement, is there an easy way to close out the draft in the winter [img]https://cimg2.ibsrv.net/gimg/www.doityourselft.com-vbulletin/1500x2000/window_1_f2279568611d1a490e51074340089648a0a9e48f.jpg[/img] [img]https://cimg3.ibsrv.net/gimg/www.doityourselft.com-vbulletin/1500x2000/window_2_b9c4b35037b8459b2e4c4d22897c514167eb4108.jpg[/img] Thanks