How far/how much gas are you using "once a month or so"? And what kind of home "improvement" items is he spending on?
You don't have to go to Dave Ramsey's class to recognize that you need to do some compromising. What is typically recommended in a budget like that is to have a list of priorities that you go down, as to how the "extra" money is spent.
So you have to sit down and write out your list. You and husband together.
What is on that list? Anything really, that isn't a regular monthly expense/bill (not groceries, car payment, etc).
So:
saving to buy a new car
buying a new lawnmower
replacing the broken edger (or getting it repaired)
trip to visit extended family
new patio furniture
new dishwasher
new bedspread
sod
bricks/mortar for a new landscape focal point
replacement American Flag for the faded one
etc
You get the idea. And you "attack" that list with whatever "extra" money you have. If you have big ticket items you are saving for (like a car, for example) then you might list a dollar amount for that item that you would "apply" to that long term item out of the "extra". So... $400 not specifically allotted to any one budget item (extra), means (for example) $200 towards saving for a car, and $200 for ______.
You can always address changes to the priorities list. You will always have to find compromises. Maybe you BOTH need to cut back. You cut down to every OTHER month, and he cuts down on frequency of projects.
If your family is far enough away that it takes an entire tank of gas, does that mean it is an overnight/weekend stay each time? Because if it is, once a month does sound pretty frequent. If you both are fine with that, great, it isn't my business. But it doesn't sound like HE is fine with it. And I would probably tend to agree with that, unless there is something more special about these visits (serious illness, bridal showers/weddings/baby shower/birth of a new cousin, 50th wedding anniversary, etc).
Some compromise is in order. Both sides.