There's Magic Long Bow's, good exp and only buy for med, trust me, it will buy. sooner or later.
And another, is Maple Long Bow's (u),
If you got good money, or really want to get your mage up,
do Adamant Plate Bodies.
Buy for Med only.
yew longbows
To be honest with you, you shouldn't really lo-alch anything since it would be a waste of runes or/and cash spent on those runes, unless you make platebodies steel+ yourself, then low alch them.
Adamant Platebody
No, you still do lose a bit.
I recommend high alching items like maple longbows (u) or yew longbows because when you alch them they gives you more coins than if you sold them.
I think you can alch it and get profit.
no, have to wait til midnight gmt
Level 56 would be good and you can alch adamant platebodies for a profit.
No, any item gives the same exp.
It doesn't matter where you alch, just alch anywhere: If you want something to watch whilst you alch: Go Castle wars or a place like that. If you want peace and quiet: Go to a place like Mos' Le Harmless, or the elven place, where not many people have access to. If you want someone to talk to, visit a friend or go to a POH and do your alching.
You cannot alch a Dungeoneering item.
It all depends on what your level in magic is, and if you are casting the high alch or low alch spell. If I were you I'd use a runescape calculator. Here are 2 calculators below I like to use. I hope you find this useful