Hello KCWells and welcome to you... you have chosen wisely in joining this forum, as it has so many helpful and friendly members, as well as a massive amount of helpful information hidden behind the button in the green strip at the top of the page
Quick answers (and I ma sure you will get lots)
1. You can suppress weeds with sheets of cardboard weighted down so they don't blow away
2. Green manure can fit into any part of a crop rotation as it suits you. Choose something suitable for the time in the year you are going to sow it
3.Tomatoes and cucumbers like warmth to germinate so get these going indoors, somewhere warm and bright
ut not too early, because they need a minimum temperature at night of 8-10 degC or they get too cold and stop growing, so work backwards from when this is likely in your area. I keep mine warm and well lit until mid-May so don't sow these ones until early April. Don't be fooled by the folk who have heated accommodation for their tomatoes, swing them this month!!