Good questions! Just checked the save quickly...
We are at the happiness limit, Globe is due in 16 (think we could MM for quicker Globe but slower growth) so I think its probably worth letting it grow into unhappiness until then. We have two axes over near Cuman which is enough to defend it from Peter, and it also has horses hooked up. JerichoHill has done an excellent job!
I noticed that Cuman is producing a worker, does this mean that Peter is too far from them to be a threat, otherwise they would be producing military? We may have to wait for them to get a border expansion before they start sending military units (one at a time

) towards Peter.
When Globe finishes we should run some scientist specialists to boost our great person production for adding to London, national epic will also help this when lit completes but again needs to balanced with military builds. (if we can generate some Great Merchants later too it would be awesome as they get +1 food) But yes, we should
definitely start going after Peter before he grows any bigger. We may need to raze some of his further cities and hope the barbs take the closer one, use some HAs for pillaging resources too.
Great point about the suicide cats, I hadn't considered that. I think we can work around the possibility of giving the AI free promotions. If we suicide one less cats than they have units, then follow up with attacking units we might destroy the units that would otherwise be promoted. Maybe.
20 turns with once city is good as mentioned previously, feel free to play less at need but in multiples of 5 preferably.
Btw Berlin was fantastic, so much history, culture and just vibrancy to the place, could easily have stayed a couple of weeks without getting bored! One of my favourite European cities. (replied to your PM Pvblivs

)