I am also asking for advice, what would be the best to put on my fire warlock for ETH Andy merc as stone? ED% or Fire%?
Don't know which one will boost me more.

https://forums.d2jsp.org/topic.php?t=109821397&f=271&o=0#p692286242 -> Protector's Stone 47ed/-10/5xp/46eg/28mf

got also some lower (50ea):
Protector's Stone 34ed/-6/4xp/45eg/15mf
Protector's Stone 35ed/-7/4xp/44eg/20mf

Physical Protectors stone colossal jewel
50% ED, -8 Phys Res, 5xp, 49gf, 29 mf 300fg
39% ED, -9 Phys Res, 5xp, 36gf, 19mf 220fg
34% ED, -10 Phys Res, 3xp, 44gf, 31mf 200fg
33% ED, -8 Phys Res, 3xp, 41gf, 31mf 120fg
47% ED, -6 Phys Res, 3xp, 29gf, 29mf 60fg
36% ED, -6 Phys Res, 3xp, 42gf, 26mf 40fg

So which should I put to Eth Andy as for merc for fire warlock? ED or fire?

fire jew on merc will not impact anything, ed is your solution or 15 ias xx fire res jewels.

his -res/+dmg won't apply to your skills, so use a protector stone

protectors stone (physical): 44edmg/-10res/4xp/34gf/15mf - 450fg
protectors stone (physical): 39edmg/-10res/4xp/27gf/19mf - 330fg
protectors stone (physical): 43edmg/-7res/5xp/36gf/22mf - 140fg

-fire doesnt help merc.. i would use ed

i have 2.. ill do either for 100

+42ed / -8 phy / 3xp / 45eg / 19mf
+47ed / -7 phy / 4xp / 34eg / 17mf