Yes. You can work on both companies. You don't need a business license as such. You need to update your permit to being employed as an independent (if you choose that route, but it's probably the easiest).

Your best bet is to do it as an independent. You do not need to register for VAT until you make over CHF75K per year. For the "handy man" gardener, I don't know if you need some type of certification. Your best bet is to go talk to the people at the registre du commerce in Moudon. They will tell you everything you need to know. But, you will need to speak French (bring someone who can translate for you).

You can import all your items, but you may need to pay import duties and customs charges for amounts over x and for food follow the labeling requirements.

I hate to say it but: there are plenty of links that tell all of this. I know Richard have even, at one point, provided a link that discusses import categories and tariffs.

Find user "Richard" and look through his posts.