This necro is problematic mostly because the information in the rest if the thread wrong/outdated by now. Especially that OP with the nice tables 'n all.
So yeah, better indeed to find a more recent one, or start a new one.
You're wrong on a couple of points:
Walking is NO heat, Running is 5. Can't Run and Fire.
Jump Jet (max) heat is 5, plus 5 per JJ. (Except for the 8th, which only adds 3)
"The threshold is 50% + 5% per point of Guts of the 'Mech's heat capacity'"
Uh, that was from back during the Backer Beta, which was supplanted by ... what you wrote 2-4 lines below that.
As for changes since before the Necro:
Coolant Vent is a 'new' 1.3 ability, replacing Juggernaut.
Weapon heat was rebalanced all over in, I want to say 1.2?, but the biggest impact was for the energy weapons.
SL costs 6 heat, ML 12, LL 18. PPC 35 (From 5/10/30/40 at launch)
Autocannon heat was adjusted slightly as well. 4/8/12/24 (From 5/10/15/25)
LRMs 6/10/14/18 (From 6/12/15/18)
SRMs 4/8/12 (From 6/8/14)
Biggest takeaways: Boating ML is bit harder now. LL pretty good. PPC useable.
LRM10 is still the 'worst', but only marginally so. LRM15 is now most efficient.
SRMs don't favor the SRM4 anymore.
Stability got a rework as well, but I'm not a 100% on how it works nowadays. Weight class enters into it.
Pretty sure Jumping lowers stability a lot less than walking/or running. (Not sure if old or new)