There is an excellent book on the Delaware Regiment by Christopher Ward, The Delaware Continentals 1776-1783. It was published by The Historical Society of Delaware in 1941. It is both excellent and thorough.
I would also highly recommend the Journals of Robert Kirkwood and SgtMaj Seymour.
For casualties, see Howard Peckham's The Toll of Independence: Engagements and Battle Casualties of the American Revolution. This gives total casualties for the engagements, and not by unit, unfortunately.
For unit strength reports an excellent reference is Charles Lesser's The Sinews of Independence: Monthly Strength Reports of the Continental Army.
Examples:
-May 1779: 242 all ranks present and fit for duty.
-March 1789: 220 all ranks present and fit for duty.
Unfortunately the returns are only for the Main Army and certain other units. Gates' and Greene's returns for the Southern Army are not included.
There was no 1st Delaware Regiment. As there was only one Continental infantry regiment from Delaware throughout the war, it was entitled 'The Delaware Regiment.'
There were not '2 different units' but only one after Camden, being two companies commanded by Kirkwood and Jacquett. Both were assigned/attached to the 1st Maryland Regiment.
From The Continental Army by Robert Wright, 273:
'Authorized 9 December 1775 in the Continental Army as the Delaware Regiment. Organized 13 January 1776 to consist of eight companies from Kent, Sussex, and New Castle Counties. Assigned 27 February 1776 to the Middle Department. Relieved 5 August 1776 from assignment to the Middle Department and assigned to the Main Army. Assigned 25 August 1776 to Stirling's Brigade, an element of the Main Army. Relieved 1 September 1776 from assignment to Stirling's Brigade and assigned to Mifflin's Brigade (redesignated 8 October 1776 as Stirling's Brigade), an element of the Main Army.'
'Reorganized 1 January 1777 to consiste of eight companies. Assigned 22 May 1777 to the 1st Maryland Brigade, an element of the Main Army. Relieved 22 July 1778 from the 1st Maryland Brigade and assigned to the 3d Virginia Brigade, an element of the Main Army. (Captain Allen McLane's Company assigned 16 December 1778; relieved from assignment 13 January 1779-see 2d Partisan Corps.*)'
'Reorganized 12 May 1779 to consist of nine companies; concurrently, relieved from the 3d Virginia Brigade and assigned to the 2d Maryland Brigade, an element of the Main Army. (2d Maryland Brigade relieved 5 April 1780 from assignment to the Main Army and assigned to the Southern Department.)'
'Reorganized 3 September 1780 to consist of two companies. relieved 1 January 1781 from the 2d Maryland Brigade and assigned to the Maryland Brigade, an element of the Southern Department. Expanded in the summer of 1781 to consist of four companies by the reorganization of two companies at Christiana Bridge.** Reorganized 4 January 1782 to consist of two companies.'
'Furloughed 17 January 1783 at Christiana Bridge. Disbanded 15 November 1783.
* Captain McLane's Delaware Company was assigned to the 2d Partisan Corps (Lee's Legion) as the 4th Troop.
**Christiana Bridge is in Delaware.
From the Encyclopedia of Continental Army Units by Fred Berg, 37-38:
'On December 9, 1775 Congress authorized a Delaware battalion and in January, 1776 Colonel Haslet's Delaware Regiment was accordingly accepted into the Continental service. Haslet's Regiment served with distinction though the year. Haslet, himself, was killed at Princeton, but under his successor, Colonel David Hall and a cadre of Haslet's former officers, the regiment was rerecruited and reorganized for the 1777 campaign. Through the years Hall's Delaware Regiment maintained its reputation. Although in 1776 the entire regiment wore the cap associated with light infantry, the author has yet to find any contemporary evidence the whole unit was intended for that role. There is reason to believe, however, that in 1776 and 1777 before all Continental battalions had light infantry companies, that the Delaware Regiment did have one of its companies trained in that capacity. The disaster at Canden on August 16, 1780 shattered the famous regiment. Most of the regiment's men were killed or captured in that battle. Afterwards, the survivors formed two companies under Captain Kirkwood and were assigned to a mixed Maryland-Delaware Light Infantry Battalion…after October 30, 1780. At Guilford Courthouse on March 15, 1781, the Delaware men formed a flank detachment for the front line and suffered further casualties. By late 1781 a few recruits arrived to strengthen the tiny remnant of the old Delaware Regiment to 4 companies. On June 13, 1782 General Greene assigned the regiment to LtCol Lauren's Light Infantry Corps. The Delaware men were furloughed soon after June 11, 1783.'
The best references I have found for the Delaware Regiment are the afore mentioned (in a previous posting) Military Uniforms in America and the above references The Continental Army and Ward's history of the regiment which is quite extensive.