West highland terrier puppy - questions!

My partner and I are wanting to get a Westie puppy next year and I want to make sure that I am fully prepared! Whilst owning a variety of pets in the past (rabbits, hamsters, cats, horses! ) We have not owned a dog before and I had a few questions I was hoping someone could help me with:

1. I've read that skin allergies are quite common with Westies - does this result in discomfort/loss of hair/dry skin etc.? And how common is this across the breed? Would anyone suggest a particular dog feed brand that prevents allergies? It it better to use a normal dog food e.g. Pedigree's and use supplements, or to use a breed specific dog food just for Westies?

2. My partner works 8am - 4pm and I work 9am - 5pm. I only work 10 mins from our home so I am planning on going back home two weekday lunchtimes myself to walk the Westie and using a dog walker for the other three weekday lunchtimes. I like the social aspect of the dog walker too as the Westie would be taken on a "group walk" with other dogs. Is this acceptable for a Westie? I've read that they are ok by themselves for 3 - 4 hours at a time and am reading up on how to avoid separation anxiety.

3. Crate vs Dog Gates - When we are at work we don't want the Westie to be "free-range" around the apartment. Would anyone be able to advise on if its better to have a large dog crate with room to move around in, or to buy dog gates and fence off a portion of our living room for the weekday hours when its by itself? I've heard that dogs like to have their own "safe space" in a crate? This would also be for night-time too.

4. How much exercise will a Westie need - I am aiming to walk the Westie for 20 - 30 mins before work, 15 mins if I'm home/1 hour if with the dogwalker at lunchtime, and then a 45 min - 1hr walk in the evening? At weekends this would change to several 45 min - 1hr walks a day. Is this enough exercise for a Westie?

5. I've read that its unwise to let Westies off the lead during walks as they are terriers and might bolt for rodents/birds. If off the lead training is started right from a puppy are they ok to be let off the lead in later life too?

6. I've read that Westies need to be brushed every day and taken to a professional groomer every 2 - 3 months for a trim. I want to avoid skin problems and not over-wash the Westie - how often do people wash Westies (even if its just the legs and feet). On the question on grooming, what is healthier for the dog - to be lightly trimmed but still quite (cutely!) scruffy/long-haired, or to be trimmed down near to the softer undercoat? Is there also a specific shampoo that Westie owners would recommend to avoid skin problems?

Lots of questions! I would be so appreciative and happy if I could have some responses! Thank you!