Final time: 2 days, 3 hours, 32 minutes. Start by upgrading research fully getting each upgrade as soon as possible staying at the research facility as much as possible, constantly researching while reloading or while enemies are dead, Next is reload time, Buy the handgun as soon as you can for more shots and only shoot enemies when they are near you until you complete reload speed then you go after accuracy, afterwards, money, buy the sniper when you can and after those upgrades you go after plant growth, ignoring the health upgrades because you can always buy health, once plant growth is maxed, you raise the plant the same way you did research, and while fighting the final boss you use the sniper rifle on everything until you can buy the x-ray gun and then KILL IT WITH FIRE... er... RADIATION!!!!!
same as the last person, i have 1824 (10 more) on normal difficulty survival on the manor and hard is still locked when it was supposed to unlock when getting 1500 as the high score