Here is the newest version of my House Rules. If you don't care about the minor tweaks and just want the solo rules, they are copied below.
Optional Rules for Solo PlayRolling Stats
Roll 4d6 and drop the lowest result for each stat, and arrange as desired.
Damage is rolled as follows:
1-5: 1 point
6-7: 2 points
8+: 3 points
Healing is rolled the same, just with “backwards” damage
All PCs have a fray die they can roll once per round, automatically hitting enemies that have HD less
than or equal to their level. Fighters have a d6 fray die, all others have a d3.
Monsters have hit points equal to their hit dice. Damage spills over to nearby enemies (both with fray
dice and normal attacks).
Death and Dying
If a character is reduced to 0 HP, they are on Death’s Door, and every time they take damage they must make a saving throw or die.