I've been using Scarpa HS12 Footwear cream for around 10 years. Treat all my leather footwear with this. Water repellent, i ahve one pair of scarpa boots that aren't goretex or anything, they've never let water in with this.
Repairs for footwear I've always used Shoe Goo, from repairing trail running footwear splits, sealing worn out holed undersole motorbiking boots to leather to boot seal joints. Shoe Goo is flexible once dry and can be used to repair almost anything boot/trainer related.
These are both the products for repairs and maintaining footwear kit I use.