Speaking of the FOV option, I just set it to 110 HFOV (your FOV in MW). Notice that cl_fovScale 1.55 is 123.268762 HFOV which is a big increase. In this case (as every time that the FOV changes), you can only maintain one aspect of your sensitivity and that's why it's recommended to keep your FOV constant across all games if possible. If you want to stay on 123.27 hipfire HFOV, you should try 360º distance (your link does that) or MDV 125% (because you're used to it for scopes) and see which one feels better (I'd personally try to avoid this situation). One more thing: if you're used to 110 Apex in-game FOV, you could try to set that in other games, but it's likely that it'll be out of range in most of them.
Regarding the scalar_0 value, it affects 1X Scope / ADS (SMG, SG, Pistol) and ADS (AR, LMG, Sniper) at the same time, but these two groups have different FOVs, so there should be a separte multiplier for each of them. When you select "All" in the conversion, the calculator will give you the value of the scalar_0 for AR, LMG and sniper ironsights FOV, but if you want all the 1X scopes and SMG, SG, pistol ironsights (except RE-45, which has its own ADS FOV value) to be correctly matched, you should use another value that can be calculated here:
-If you used 360º distance for the hipfire conversion
-If you used MDV 125% for the hipfire conversion
ProuDBeasT's post in Conversion Problem: Relative aim to Apex Legends (from MW) was marked as the answer