Hello Allan
Welcome aboard!
I'm afraid the news is not good. There are only two restaurants within the 3km range you mention. The first and best choice is the excellent Rouselles at the Tobago Plantations Golf Club (although don't hold your breath - I tried to get dinner reservations there three times during our recent trip and each time the restaurant was closed for private functions. They are open for breakfast and lunch and only recently started opening for dinner. They are a 5-10 minute walk from the hotel.
The second choice is the Garden Grill at the Ocean Point Apartment Hotel, which must be about a 15 minute walk from the hotel. VERY mixed comment about this place.
Actually, thinking about it, Lambeaux is probably not more than 3.5km if you walk along the beach. You would then have the choice of the Inn On The Bay or the Cat & Fiddle, or another 5 minutes up the road, the excellent Shore Things (daytime only).
Yes, you will need a torch. The grounds of the Tobago Plantations golf course do have some low-wattage lights marking the road, but there is no street lighting in that area outside the grounds. Frankly, I think that you will find that you are strictly limited to Rouselles for evening dining. The Hilton is surrounded on three sides by the Tobago Plantations golf course, with the ocean on the fourth side. Even having walked to any extremity of the golf course, you are in largely open country. The walking will be very pleasant, but it will be walking for walkings sake, rather than to go anywhere. I would budget to have a car for your entire visit.