adjusted knowledge - I resided in the Philippines decades ago for a short period of time.
I know the boxes that you speak of: the balikbayan boxes. They have a set rate. Usually one price for Metro Manila; higher if the box is going to one of the many provinces and islands there in the Philippines. Regardless of the weight, yes ... just as you speak of. I've seen some of those boxes weigh several hundred pounds. You'd swear someone was shipping bricks!
I have shipped via 'Balikbayan' and made sure I itemized things (here: writing them down). When you're sending clothing items, toiletries and non electronic items, you are usually OK. My boxes (aking kahon) - arrived a bit squished, but all the items were inside, and intact. I remember sending (this is more than 20 years ago), CDs and cassette tapes, VHS/Beta tapes and even a couple of AM/FM Walkmans. They were still in the boxes and in good working order. We compared notes: everything was there. Funny thing, it was AFTER it got there, things disappeared.
I have mailed items, and I lost things almost 4/5 times. So I never send anything via mail, which I know you know is a recipe for theft and disappointment.
Any items that are electronic, I have sent with someone I know who is headed over there to the Philippines. If they have room in their luggage, I kindly ask them if they can take it over for me, usually with a little gift (baon) to the person carrying my gift.
You can give it a try I suppose, inserting some of those things like XBOX and PlayStation in the Balikbayan box, packed way inside the middle of the box. If they are unwrapped, you can also indicate IF there's a problem, that they are USED (not new). I know that there is some declaration sticker or form you sometimes have to apply to the outside of these boxes. I usually kept the descriptions general without detail. But sometimes ... officials at the Port of Manila or Cebu, may try to extort. It happens way more often than not.
I'm with JWdaughter. If possible, locate someone you know, or friends of friends who may be going, and kindly ask for them to take some items. May not get them ALL together, but maybe in a couple of trips in quick succession.
GOOD LUCK!