So ... a few things.
1. Marx distinguishes his method from Hegel's in many ways. He is clear, for instance, that for him the method of scientific discovery (i.e. the method by which we come to knowledge) is to be distinguished quite sharply from the method of presentation (i.e. the method by which we present that knowledge to others). This is a variation on the Aristotelian and Thomist idea that what is first in the order of being is not what is first in the order of knowing. Marx acknowledges that his method of presentation derives from that of Hegel, and he gives due credit to the accomplishments of the Hegelian system, granting its many shortcomings. But his method of discovery differs significantly from that of Hegel. Marx is a naturalist. His claims are not "dogmatic" or "rationalist." Every empirical claim in
Capital (i.e. all those made after the initial excursus, at the start of Vol. 1, on the logic of the commodity form, which establishes the basic conceptual framework employed in what follows) is supported by appeal to evidence. No one, having read and understood
Capital--having worked through the chapters of detailed attention to English state-administered labor surveys, for instance--will claim that its method is dogmatic. This is a claim made only by people who have not read the book. The notion that the dialectic form plays a constructive role is an artifact of Engels's sometimes clumsy appropriation of Marx's thinking, of the former's own forays into nature-philosophy (as in his
Dialectics of Nature), and of the Bolshevik vulgarization of Marx's work.
2. The thesis-antithesis-synthesis model, which is a vulgarization of Fichtean and Hegelian ideas, does not figure in Kant's thinking. I gather you are confusing two Kantian ideas. In the Antinomy of Pure Reason section of the
First Critique, Kant treats a series of pairs of contrasting metaphysical conclusions, decision between which cannot be made by reason alone because each follows validly from true premises. His proposed resolution, however, is not to
synthesize the opposed theses, but to dissolve the tension between them through the postulation of regulative ideals. Separately, in the transcendental deduction of the pure categories of the understanding (especially in the A-deduction), Kant treats of various syntheses which are involved in the logical movement from the pure, non-cognitive manifold of sensation to the conceptually thick perceptual datum we encounter in ordinary experience. Such talk also arises earlier, already in the Transcendental Aesthetic. These two notions, however,--antinomy and synthesis--are not related in the way you suppose them to be.
3. Fichte employs something like this model, but not in the rigid way you suppose. Hegel did not use the phraseology, and it aptly captures only the first few steps of his
Science of Logic. Marx's few remarks on the topic of the thesis-antithesis-synthesis model are critical, as for instance in his early book on Proudhon's vulgarization of Hegel, where he mocks Proudhon's employment of the model. It is unclear whether Marx himself believed at the time that Hegel employed the model. But it is very clear that by the time he revisited Hegel's
Science of Logic while he wrote the
Grundrisse--well before completing the first published edition of Vol. 1 of
Capital--he had adopted a more sophisticated understanding of Hegel's method as involving a movement from abstract or one-sided conceptualization to concrete or all-sided conceptualization. This movement can be compared to the movement from a simple physical theory of (say) the behavior of gasses, which treats only of their behavior under idealized conditions, employing a multitude of
ceteris paribus clauses, to a more all-encompassing theory, integrated with other physical theories, able not only to predict the behavior of gasses, but also to
explain (in more fundamental terms) why gasses behave as they do. It is this method that Marx inherits from Hegel.
4. Marx's positive program was not concerned with "the denial of property as a right." Nor was it concerned with rights at all. Marx's principal contribution was a critique of political economy, bringing out the many odd suppositions of the classical Smithian and Ricardian tradition, and identifying a number of key structural contradictions
within the capitalist mode of production. He identifies some key tensions in some of the central elements of the capitalist economic formation--in particular the category of relative surplus value, which concerns the intensification of surplus production through machine-assisted labor--which went unnoticed by previous economists. Marx identifies talk of rights, like talk of law, the good, and other ideological notions, as byproducts of underlying economic relations. And he believes that economic transformation--even of the revolutionary kind--owes its possibility and its appearance in history to economic prefiguration. Thus, though his legacy was co-opted by the authoritarian populist managerial socialism of the Bolsheviks, and from there exported to much of the Eastern world, Marx was of a thoroughly anti-populist and (basically) anti-socialist spirit. His advocacy for centralizing programs in the First International days was even then motivated by concern for economic progress, etc. This line in Marx extended, at its extreme, to support for liberal free trade and explicit opposition to socialist efforts. This because he believed that the development, within capitalism, of basic structural and class-centric antagonisms through increasing automation (as well as the intensification of labor time and ever-increasing production-side inequality between working and ruling classes) was the only way forward to a world in which large portions of the human population are not forced into harmful and alienating labor. He tended to dismiss both social democratic solutions to distribution-side inequality and utopian socialist proposals for immediate revolution as hapless instruments of the existing order, obstructing progress toward the next. For an example of explicit endorsement of free trade, see his public address to the Democratic Association of Brussels in 1848:
http://marx.eserver.org/1848-free.trade/ftrade.speech.txt