如图,\(AM\)是\(\triangle ABC\)的中线,\(D\)是线段\(AM\)上一点\((\)不与点\(A\)重合\().DE/\!/AB\)交\(AC\)于点\(F\),\(CE/\!/AM\),连结\(AE\).
\((1)\)如图\(1\),当点\(D\)与\(M\)重合时,求证:四边形\(ABDE\)是平行四边形;
\((2)\)如图\(2\),当点\(D\)不与\(M\)重合时,\((1)\)中的结论还成立吗?请说明理由.
\((3)\)如图\(3\),延长\(BD\)交\(AC\)于点\(H\),若\(BH⊥AC\),且\(BH=AM\).
\(①\)求\(∠CAM\)的度数;
\(②\)当\(FH= \sqrt {3}\),\(DM=4\)时,求\(DH\)的长.